This thread is becoming very interesting - lots of tricks!
So there goes another one:
I have a very simple enlarger - Opemus III, no filterhead, etc.
Using VC filters is not a problem - they can be placed between condenser and neg carrier - but no ND filter...
Yesterday I've just installed a standard light dimmer inside my EPOI enlarging timer (sure, one can use an external unit - but this way is neater) so the elarger lamp can be fine tuned to the light I need.