Sludge under valve covers...how do I clean that?

[Laser145]

I'm working through the engine on my 87. Pulled off the valve covers and there is sludge everywhere!!! Black,oily, messy, sludge!

Whats the best way to clean this out? I'll use a spoon and screwdriver along with my 10 dirty fingers to get a lot of it... but eventually I'll want some solvent.

What is safe to use? I don't want to damage anything below when it runs down the galleys at each end of the block.

Cheers
Taylor