Did this get solved?
We almost always pressure bleed brakes/clutch on all our cars. We have an assortment of reservoir tops with air quick connect fittings. Dial the air pressure down to 3-5psi, screw on the cap and bleed. Makes it a quick one-man operation.
On the race cars we do it the same, but then start the engine, let it warm up, then do a normal pump-release 2-3 times for each slave. It seems that sometimes there is a stuck bubble or two and the vibration from the engine can free it up.
I did have a similar clutch problem on the SLC. Everything was fine on Friday, then Saturday morning fired it up (it was cold overnight), headed to the starting grid. The clutch felt wonky. Gear shifts where clunky. On track the clutch would slip at higher RPMs/Full Throttle. So seemed like it was not full engaged or disengaged. Pulled the trans, all looked OK. Put it back together and it was fine (after being bled of coarse). Never really figured that one out. Do carry a spare master cylinder in the trailer now.
If anyone needs a WILWOOD reservoir top to make a power bleeder, PM me your address. I have a box of them laying around somewhere.