Hey Chuck,
the flame maple veneers are thin, so I would recommend a black stain and rub back, don't do any pre-sanding before the stain.
Once that is carefully sanded back (I'd use about 240 or 320 grit), then apply the walnut stain to the veneer.
Rest of the basswood body (sides and back) would probably be worth using ebony timbermate will bring out the grain, sand off then walnut stain.
Make sure your friend starts a build diary, keen to see progress !