george I can give you some insite, but I need to know if your working in polyester or epoxy? All of my work is in epoxy.
http://www.classicmako.com/projects/xshark/
My hands have been bleeding from all the blocking that I have been doing. I've added LOT's of square footage to be sanded to this boat. [img]/images/graemlins/grin.gif[/img]
I don't recommend any of the single part spot putties that 3M makes that you will find at the auto body stores. That stuff shrinks to bad. A 2 part is better, but I use Interlux's watertight epoxy for the little nicks and System 3's Quik Fair for the large area's. Forget mixing epoxy/microballons/cabisol. It's to slow and pinholes to bad.