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?