if you are sealing/glassing while using a variable heat source more than likely you'll cause outgassing as one area is heated up and another is cooling down. For joints it's not as big of a problem but I wouldn't want to risk bubbles showing up by heating an area up,,it outgasses,,apply glass/epoxy,,it outgasses,,,move to the next spot that's being heated up...maybe you could do it but the risk is the wood still outgassing for a few minutes after you remove the heat or an adjacent glassed area heats up as the lamps are moved around. I'd try and get the whole kayak heated up, wait a few minutes,glass it,,then walk away.