Restarting AC in 79 chevy with Freeze-12

I have a 79 chevy 1/2 ton with a 350 and factory air. I bought this truck cheap just a few months back from a kid that really didn't use it- he has a newer Z-71. He had bought it cheap from his girlfriends father 8 months earlier and thought he might tinker with it. He works at an auto parts store so he didn't have time, and since he wanted to pay off some debt, I now own it.
I want to get the AC working again. The only thing that has been done is that the pressure switch has been disconnected so the compressor won't try to come on. If I push in the low side schrader valve, there is still a small amount of pressure in the sytem, which to me means that the sytem is in pretty good shape with out any severe leaks - to be able to hold pressure since 79. I was told that the freon got too low to cool anymore and that the older guy that had it, didn't want to spend the money to put new R-12 in it so he unplugged the pressure switch. Because the system seems to be in good shape, this makes sense to me.
I plan on putting some of this new blend refigerant in it. I think it is called Freeze-12 and is a blend of 134 and R-12. I'm told it works a lot better than the 134 conversions that only half-ass cool on an old R-12 system.
I've been told to turn the compressor over by hand to get the inside oiled, before I get it cycling again. I was wondering if anyone knew of anything else I need to do so I don't lock it up or damage it?