I clean with CLP first, then put tetra grease on all the contact points on the bolt, 2 lines on the receiver channel and the 2 lines on the top cover. Never anything in the lower. I like the grease because it stays on the point of contact and doesn't run. The wear spots on the UZI are very specific. If you oil the whole inside it will just make dirt, carbon, and brass fragments stick to everything.
If I'm shooting in the cold, I go light on the grease because it makes the bolt bind and do funny things.
I highly recommend using grease.