Is there an ideal size and thickness for a pick for playing funk music?
Whatever you feel comfortable with. You should be able to get the sound you're looking for with any pick, you've just gotta feel it.
picks are preference. that's basically what this threads gonna end up saying. for funky stuff i use like a .73mm or yellow tortex the .73mm probably aint right, but its around there.
with picks, theres really no advice that can be given. im a metal guy and i know all kinds of guys that use the same picks and i know other metal guys that like completely different picks
For the typical funk guitar sound, a thin pick would probably work best since it would give you that natural attack.