hmm, guitar for reggae and ska are sometimes actually easier to learn on acoustic in my opinion- thats just me though.

so heres how it works for ska-

on the downstroke, have you fingers in the right placement for the chord, just have them so they are just barely touching the strings. this will make a kinda "THUNK" sound. so on the upstroke, press down on the chords to get the actual chord sound.

oh, and try not to play actual traditional chords for both of these genres.

instead of a G like this:
- 3
- 3
- 0
- 0
- 2
- 3

play one like this:

- 3
- 3
- 4
- 5
- 5
- 3

see, its the same thing, just in a power chord. when you play it like this, the downbeat "THUNK" wont have any open strings to mess it up.