[header] How to soften a toothbrush [title] Run it under hot water. [step] Holding your toothbrush under hot water is one of the most effective ways to soften your bristles. As the water heats the bristles and gets absorbed in the fibers, it will soften them and make them more pliable. 
[substeps] Hold the handle of the toothbrush so you won't burn yourself. Let your tap water get hot, then put the bristles under the tap.