The DPO painted the pop-top with brush-on house paint, so I've started 
sanding it to remove that paint. I tried other techniques with no 
satisfaction. The air sander makes a relatively quick, easy job of it.

Sanding takes a layer of fiberglass off; how much depends on how deep you
sand. What you end up with, however, is a relatively smooth, clean piece
of fiberglass. I suspect that without using some sealer or high-quality
marine paint, I'll end up with the dreaded mildew/dirt lines in the
microgrooves left by the sandpaper...so I'll use some of the rubberized
paint mentioned in the archives, though I may put it off until Fall, since
I'm considering options for a permanent canoe rack. I thought it worth
mentioning, however, that sanding is an option for those who wish to get
their tops clean and don't mind losing a little fiberglass.  8) Joe