: Is mineral spirits ok to use on sanded FG to wipe down prior to a
: fill coat of epoxy? I'm trying to figure out why the fill coat
: does not want to level out nice. It goes on ok but after a few
: minutes it forms an orange peel texture.

Short answer: NOOOOOOO!!!!!
It is a petroleum distillate and contains paraffins and will cause orange peel dimples.
Use soap and detergent to cleanse your hull and then wash off thoroughly.
You can use alcohol if you must.
JohnK