: Brian, as a soon-to-be-owner of my first nylon/varnish skin, when things like
: this happen and touchups are necessary, what sorts of issues do we pay
: attention to with regard to adhering the new varnish to old? Do you just
: sand lightly and re-varnish that area?

It's more important that the area is chemically clean, but a light sanding won't hurt.

: Is it important to use the same varnish as originally coated with?

Only if color matching is an issue.

: Are there compatibility issues?

No. Once cured, varnish is inert. You can coat it with pretty much anything.

: Does the area need to be cleaned with anything special, or is a soap/water
: washing good to remove any oils or residue that might interfere with
: adhesion?

I rinse with water to remove salt residue and other water-soluble materials, then clean it again with lacquer thinner to remove any oily residue. Lacquer thinner will soften the top layer of the varnish, so don't get too aggressive with it.