Greg Guarino wrote:
Not exactly woodworking, but ...

Two custom-built wooden exterior doors have developed cracks in the
paint, mostly where the original pieces of wood were joined. The paint
has flaked off to bare wood in those areas, leaving maybe 1" exposed,
but the rest of the paint is in reasonable shape.

We're having a guy come paint the door (this is a commercial building,
not my house), but he's a handyman at best (I didn't pick the
workman). We'll have to guide him.

After scraping away the cracked paint, what can we do to smooth the
edges that are left, and prep the door for (primer and) paint? Do we
sand down the edges? Or "putty up" the low spots? Hand sanding?
Sander? Grinder with flap disk? Something else?

1. Hand sand the areas with a hard rubber sanding block. The goal is
twofold: 1, accomplish some but not all feathering and 2, primarily, to
renew the weathered surface of the exposed wood.

2. Get a tube of fairing/body purtty at Napa or other similar. You could
use Bondo but the putty is easier to work with and MUCH easier to sand. It
is basically talc and lacquer so if you have the ingredients you can make
your own.

3. Apply the putty with one of those credit card size, flexible plastic
spatulas used for bondo. The goal is to fill low areas. When dry, hand sand
the areas with a hard rubber sanding block. Repeat if necessar.

4. Prime and paint.

BTW, the paint will probably eventually crack again at the joints