: it is a bad or good idea to use spray foam insulation into the bow and stern and not use the air bags? The foam floats and is not very heavy.

Chris,
I've got a fiber glass Sailfish type (10' LOA) boat back in the woods that has a urethane foam core for floatation and strutural rigidity. It weighs about 300#. Yours free. If you want rigid foam flotation look for Dow's Styrofoam. This comes in 10'L.X 10"H.X 20"W. billets and is often used for dock floatation. A billet goes for about $70US. The billets are not very strong and break up. You can probably find what you need on the lee shore of any recreational lake or around a marina dumpster. I collected enough this way to put four inches of insulation under the 1100 sqft. concrete floor of my shop. I like warm feet!

: I also want to paint it can you use spray paint? What kind? Color?

There was a thread here a few days ago concerning the use of auto finishes. Look for that. If you want a first class job do the prep yourself and have an autobody shop do the spraying with whatever they have in the gun.

In any event you have to prep the hull. First you must carefully remove all surface contaminates with a solvent like acetone. Then the entire surface must be sanded to remove any glaze from the gelcoat. Any surface damage or unfairness should be filled with a high quality filler and sanded fair with the surface. The fanatics like to get down to 1600 grit before they quit, but I feel that 250-300 grit will produce as fair a surface as your paint will obtain and anything more is not productive. I like to use WEST 410 firing additive with epoxy or polyester resin as a filler. A final solvent wash and you're ready to paint.

Yes, you can use any decent acylic enamel with appropriate primer, but now that you've put all this work into the hull it's worth using a superior auto finish. If you don't want to go to that expense and want a high quality DYI job look into Interlux's brushable Brightside one-part (non-catalysed) urethane.

As for colors, if you properly prep the hull you can use any color you want. Dark colors will betray any unfairness in the hull more that light colors so if you're not confident of the prep go with white.

Just my opinion.
Geo. C.