Do you need to remove a bunch of burnt-on stuff as well as the season?
If the pan is clean but not rust-resistant or non-stick like you want, I'd suggest just treating it like you were doing it for the first time and just season over the old.
It's not like you care about hurting the old season--you'll just be thickening it and filling in gaps.
If you need to get it back to day zero, there are definitely questions here with good answers about how to do it.
But the first thing I'd try, since the day zero cleaning methods are fairly drastic, is to make sure it's as clean as you can manage, then just go ahead and season.
I have had good luck rehabilitating pans that were poorly seasoned but otherwise OK by doing this.
Based on your response in the comments, I would definitely heat up the pan in the oven as high as it will go, and let it go until it stops smoking (put the cold pan in the cold oven to start).
That should burn off/dry any excess oil, which it sounds like you have.
Then I'd let it cool enough to handle, then season as if it were new.
I don't care for the "tacky" seasoning because it's too easy to get a buildup of unseasoned grease.
So I'd cook that down/off and start over.
And I always rinse with the hottest water my sink makes, to prevent buildup--no soap, though.
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From what you're describing, you probably just need to clean it (maybe a little scrub; I use some coarse salt and oil) and re-season, not fully strip it ... ...
but you have a nasty, disgusting pan ... the sort of thing that's found when cleaning out someone's barn or otherwise neglected for years, first start with one of: self clean cycle of an oven fireplace (once the fire's going well, just set it in the hot coals, and leave it 'til the next day) campfire (pretty much the same thing) grill (if charcoal, follow the fireplace rules; if gas, just crank it as high as it'll go) Next, you'll need to scrub.
A wire brush is your friend for this.
(I have some finer steel wire brushes and brass wire brushes; the heavy duty steel ones for scrubbing paint off of concrete block might be a little rough on the pan; a grill brush might do okay).
Then wash, dry, heat and just season it as if it were new.
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Scrubbing is hard.
In general, burn it off.
You have to get the pan super hot, and it will have to stay hot until the carbon (oils and food bits) turn to ash (white).
This takes awhile.
You can stick it in a fire.
In my restaurants, we stick it over a vey big flame.
For the home, you can flip it upside down and put it in your oven on a self cleaning cycle.
The clean mode is HOT (800 edges?)
and your pan will come out clean.
Easy.
Just remember to REMOVE the racks, otherwise they'll get destroyed.
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You could also take your pan into a sandblasting company and get it sandblasted.
That will leave you with the grey/silver cast iron like when you get it new.
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To strip seasoning just heat it up real hot, or throw it in the fire for a couple of hours
You should be able to re-season a pan as often as you like
You should have to ever do this unless you don't look after it (let it rust, or use vast amounts of vinegar etc
The best seasoning is one that is built up from many thin layers over many years
Flax seed oil is fine, so is practically any oil, the oil gets converted by the heat into a polymer of sorts, so the exact type is somewhat irrelevant If you seasoning is sticky, just heat it up hotter till it either sets or incinerates off
That's the beauty of cast iron, you cant go wrong.
More heat will always fix the problem :-)
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My preferred method is lye.
Strips the seasoning without hours of playing around with sandpaper.
Soak the pan in strong lye overnight, then wash with lots of water.
Take precautions while working with lye (NaOH), the stuff is very corrosive.
Don't use acids on an iron pan, they rust the surface in seconds.
(So no barkeeper's friend!)
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Oven cleaner, a very heavy black plastic bag, preferably a warm day.
Get bag.
Home Depot sells Contractor Bags.
Spray
a bunch of oven cleaner in the bottom of the bag.
Drench
the Cast Iron in oven cleaner.
Put in bag.
Leave it in the sun all day, sometimes 2.
Clean it very well.
Re-season it.
I have put a pan in the bag this way and left it in the back of my truck.
2 days later it came out of the bag looking like it was just cast.
cooking.stackexchange.com/users/68059/Brian
I read the same article and immediately stripped and reseasoned my #7 Griswold.
I mainly focused on stripping the cooking surface (not caring as much about the sides).
I alternated between scrubbing with Barkeepers Friend and a scouring pad letting it sit on the burner on high heat until all the crap turned to dust.
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Sandpaper, works like a charm.
Just takes a little persistence, and then a thorough washing to get the fine bits of crud/iron out.
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After reading  this article , I want to try to re-season a skillet with flaxseed oil; I'm fairly certain I did a terrible job when I seasoned the skillet several years ago. Is it possible to do this with steel wool or vinegar? (I don't have a self-cleaning oven, so that method is out.)
Stripping seasoning from cast iron
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It may be OK to clean it with coarse sea salt and oil and then season over the old with flax seed oil or another oil, heating it up more if the surface is sticky. You can also heat it up hotter to strip the old seasoning or take it off with sandpaper. The good thing about cast iron is that it is very forgiving to different techniques. If you want to strip the old seasoning then just get it really hot or use sandpaper. You can also just reseason the pan with heat and oil.
You don't need to strip the old seasoning, just reseason it like you did at the beginning. You can use any kind of oil to reseason. To strip the seasoning you just get it really hot or use sandpaper.