240 air conditioning refit

[Krampus]

As I have the engine compartment all torn apart to replace the timing belt and accessory bushings, I figured that now would also be a good time to properly refit the air conditioning system. I charged it with R134a (and oil) since the original R12 had long since leaked out. For my troubles, I got briefly cooler air, but it soon conked out again. My plan is to replace the o-rings in every fitting I can get to, flush everything out of the system, replace the oil in the compressor, pull a vacuum, and refill. A couple of topics I'd like opinions on:

1) What is the least expensive yet effective way for me to flush the AC system? I was looking at a kit that has a canister you fill with flushing fluid and then blow through the system with a compressed air line, but I'm kind of 'eh' on spending ~$60 on a tool I'll hopefully only use once. Do I need to completely disassemble the individual pieces for flushing, or can I just unhook it at the compressor and blow all the way through?

2) R-134a or R-12a (Duracool, which I understand to just be purified propane)? I was leaning towards Duracool, since I can get it locally, it's not terribly expensive, and my understanding is that it performs similarly to Freon. The latter is important, since I wouldn't have to crack open the expansion valve to adjust it for R-134a. Not to mention that R-134a breaks down into nastiness when it gets too hot, whereas propane's worst-case is just fire.

3) New condenser? I was looking at one of the drop-in parallel-flow ones, wondering what kind of experience people have had with them.

4) What oil should I use? Ester or PAG?

5) Do I need a new dryer? Can the existing one be "refilled?" (Isn't it a canister of silaca gel or some such?)

Comments / experiences / horror stories?

- Jack