Thanks, all. An old 35mm enlarger is a possibility but space is a consideration. I've been thinking more along the lines of boxing in a low wattage bulb or LED or (..?) with a slot for 6x6 VC filters.

I suppose if I can't get dim enough I could always drop in a Wratten ND filter.

Bouncing a few flash pops is a nice idea but I need to be able to burn/dodge so I'm looking for a wattage and distance that'll allow for 15-20 sec exposures at least. Any prior experience along these lines would be gratefully accepted.

Oddly enough, a friend from school back in the early '80s sent me a picture of our old darkroom, enlargers all gathering cobwebs. Maybe I drive a few hours and liberate a few...