Methyltransferase required for the conversion of demethylmenaquinol (DMKH2) to menaquinol (MKH2) and the conversion of 2-polyprenyl-6-methoxy-1,4-benzoquinol (DDMQH2) to 2-polyprenyl-3-methyl-6-methoxy-1,4-benzoquinol (DMQH2). a 2-demethylmenaquinol + S-adenosyl-L-methionine = a menaquinol + H(+) + S-adenosyl-L-homocysteine a 2-methoxy-6-all-trans-polyprenyl-1,4-benzoquinol + S-adenosyl-L-methionine = a 6-methoxy-3-methyl-2-all-trans-polyprenyl-1,4-benzoquinol + H(+) + S-adenosyl-L-homocysteine Quinol/quinone metabolism; menaquinone biosynthesis; menaquinol from 1,4-dihydroxy-2-naphthoate: step 2/2. Cofactor biosynthesis; ubiquinone biosynthesis. Belongs to the class I-like SAM-binding methyltransferase superfamily. MenG/UbiE family.