I actually prefer MIBK far over MEK for thinning, but it is far harder to find.
West Marine used to carry it, but no more.
There is one industrial paint supply near me that does but they now charge $40/gal.
That styrofoam dissolved in MEK sounds a lot like the plastics in commercial sanding Sealer.

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!
No Harm=NO Foul advocate

If you are NOT FLYING LOW in the left lane, you need to GET THE #$&@ OUT of it !

Yes, there is such a thing as NORMAL, if you have to ask, you probably aren't !