I ordered a can of "corrosionx" based on Scott's suggestion. He has not steered me wrong yet.
The two times I've had a regulator apart so far I've just put a very thin film of silicone grease on the washers and the regulators work well. The Huma in my Caiman come with a huge amount of what appeared to be silicone grease on the washers and none on the o-ring below the adjustment screw. So it stopped working. So I ordered a rebuild kit and while I was waiting I took it apart and fixed these issues and it works great now. I have the kit for next time. O-rings should always get a little silicone grease I think but avoiding corrosion is probably the bigger need for the washers.