MEK = methyl ethyl ketone

It will be labeled that way. Mineral Spirits is a different solvent and will be labelled "Mineral Spirits." Kerosene will be labelled "Kerosene."

MEK (a.k.a. methyl ethyl ketone) has no use as a bike solvent.

As far as tar on your bike, I've use small amounts of charcoal lighter fluid (OUTSIDE). You can buy products formulated to remove the sticky goo left behind by some merchandise price labels. They probably contain solvents you want to use in limited quantities, like xylene.

Wear nitrile gloves like all the people in those Park Tool "how-to" pictures do.