I think Resinhead has pretty eloquently explained the protocols. But as an industrial spray-painter, when I hear crap about fish-eyes, it makes my hair stand up on end.
To repeat: if you have a freshly sanded surface, don’t wipe it with any solvent. Blow it off with filtered compressed air wearing clean gloves on your hands. Beyond that I would use only a clean dry brush or a clean dry paper towel. If you do, though, make sure the last thing to touch your board is air.
As you’ve learned, it’s best to do your sprays directly on the foam.
It sounds more like you have an incompatibility issue between the paint you used and the resin.
The heat-gun suggestion applies to bubbles, not fish-eyes. Performed properly, it works wonderfuly.
It doesn’t take a clean-room to produce a clean product. It just takes a little experience and following protocol.
I, too, have spider-sense. At this point, it borders on OCD.
And I buy 3M 233 by the sleeve. I would use nothing else.