mate what gaps? all i did is fill them with filler any wood or car body filler will do!!,then yes warm up the epoxy prior to use it helps.all i do is leave it in the sun to warm up or close to a radiator as long as its runny it will work fine.im not sure about the type you have to be honest maybe try it on a scrap peice and see how it sets up.its only to seal the hull so i think it should be fine.dont use expanding foam it will split the hull apart its strong stuff.also what helps the epoxy penetrate the wood is the setting time if its slow setting it will penetrate enough to get a good hold if it drys in less than an hr it wont key to the wood very well.have you glued the curved area of the bottom of the hull yet? if not drill small holes as in w3bbys pics and use zip ties to hold it till the epoxy glue dries ,normally overnight then you can cut them off and fill any holes left and sand smooth before sealing the hull.where the sides join the hull bottom i glued 1/4 square spruce strips to the hull and then attached the sides to these it give more gluing surface .as far as paint goes i use car spray cans, first primer then the paint and use a clear coat to match to protect the paint.i hope this helps!!if you want to use a brush,any enamel will work too or some use acrylic paints also but ive never used them.if you ask at the car dealers what they suggest for paint and explain you need fuel proof paint they should be able to help with paint and clear coat(laquer).