Suitable Thinner for MM Semi-Gloss Clear?

I would think iso would work though I've never tried it.

I would use plain water for that clear coat, but rubbing alcohol might work.  

I can't recall where I read it, though I read that someone had 'determined' that Model Master thinner was 7 parts 70% USP isopropyl alcohol to 3 parts distilled (though I used tap) water, I've tried it in the past and it worked out well.