The pencil technique works well: just scribble all over the area you're
sanding and stop when the pencil marks disappear. Or, if they're in a
small depression and the area around it is white, wipe off the pencil
marks and fill.

Regarding scratches, a repair expert showed me one way to make sure the
scratches are gone before moving on: sand only in one 45-degree
direction per grade of sandpaper...and then switch directions when
moving up to the next finer grade. So if you're sanding with 600 grit
in an upper-right-to-lower-left direction, don't stop until all the
[400 grit] sanding marks/scratches in the upper-left-to-lower-right
direction are gone.

He also demonstrated how I'd been using sandpaper far too long. 400
grit cuts great, for example, when it's new, but I'd been trying to
conserve paper and working WAY too hard (and long) to get results long
after the paper wasn't cutting much anymore.

There are lots of little tricks and hints to wing sanding. Ken
Kochanski's article is helpful. It would be great if someone pulled
together the collected wisdom of repair experts and inveterate tuners
for the rest of us.

Chip Bearden
ASW-24 "JB"

Roy Bourgeois wrote:
A similar technique is used to deal with the "orange peel" that
develops
when first spraying Prestec. See Kochanski's article at the SRA
site. He
uses thinned blue dope. Also helpful: I use large carpenter's lead
pencil
to mark up the border area between old and new gel coat. When the
pencil
mark disappears - it's time to STOP sanding.

Roy A. Bourgeois