update

I think I finally found a way to smooth the hulls. Forget he putty knife. I put a flame spreader attachment on my torch, to flame smooth the hulls.

http://www.acehardware.com/product/index.jsp?productId=2564149&cagpspn=pla

As I was working I noticed the flat side looks like a red hot putty knife. It works. I was able to build the skegs back to about the original shape.

You have a hot scraper or you can melt braze rod by pressing the flat side against the braze rod and the braze doesn't stick to it. Just keep the flame level to about half and don't point the flame directly at the hulls when you use it this way.

Also I found that the 5200 I applied to hot hulls, last year stuck a lot better than when I applied it to a cold hull. See the West System Video about "activating plastic".