I'm glad the flexbond idea is catching on... this product is such a godsend when it comes to painting foam (and making sure the paint will stick to the foam).
I've never tried it (mixing it with so much paint)... but I have a friend who showed me what it looks like and I didn't like it.
I don't know how much paint he put in there and how he applied it (and that may make a big difference in the end result) but the flexbond has a noticeable thickness when cured (you can clearly see where you've put flexbond on a piece of foam and where you forgot to put some). So when mixing it with paint and giving more than 1 coat (you'll need more than 1 coat to get a "solid" color... you could see each layer of paint.
What I mean is that it was noticeable (up close) that the paint was not all on the same "level" (because of that thickness that flexbond has).
So, I prefer leaving my flexbond as is when I apply it to foam... or will only taint it a bit (maybe 10 part flexbond to 1 part paint) when I'm working with a colored foam that I know I'll have difficulty covering up with the color I'm using to paint this piece with.
I had planned to use Dupli-Color's Vinyl/Fabric spray paint (they have one that comes pretty close to the auto paint color I'm using for my son's IM hard armor).
Here is a test I did with this paint on thin rubber, craft foam and plastic. It work well on all three surfaces.
Also, here is my recent test of standard auto paint over plasti-dip: HERE
Has anyone had any luck with Adhesion Promoter products? Sorta like this BULLDOG product?
I just picked up some Dupli-Color Adhesive Promoter and tested it with a rough 3mm EVA Closed-Cell foam piece I threw together earlier this week. After 3 coats of this Adhesive Promoter, I hit the piece with 3 coats of the Sunburst Gold Auto Paint (also from Dupli-Color). Here is the result video...
As mentioned in the video, the only downside to this seems to be a slight dimpling or pot-mark pattern to the paint. This shot was done after ANOTHER coat (that would be the fourth coat) was applied to this test piece.
All in all, I think I'm using this method for the pieces I want TOTALLY flexible. I might modify this slightly for foam pieces I harden with epoxy (or Plasti-Dip).