Before I bought a recovery machine, I had a gauge set and a rotary vacuum pump. Here's how I did a recovery.
I brazed up an adapter between the 1/4" SAE flare and a 3/8" LH gas bottle connector. I vacced the bottle out completely (Ok, I have a vacstat also, so down to > 200 microns). I bought a kilo of dry ice from BOC, put it in an Eski the gas bottle fitted in and topped it up with Metho. Dropped the gas bottle in which chilled the gas bottle to ~-80C. Hook up the gauges, vac out the whole assembly. I had a ball valve on the end of the vac hose. Then connected the vac hose to the "very cold" bottle and opened all the valves. That sucked all the gas out of the system and into the bottle. _all_ of it.
I could weigh the bottle before and after which gave me the refrigerant weight +/- 1g (I have $40 35kg shop scales that are both accurate and calibrated).
To get the gas back in, hook the stuff up, vac out the system and gauges, connect it to the bottle and turn the bottle upside down. Open the high side valve and let it suck as much liquid in as it can. When it has stopped, shut the high side valve, start the vehicle and slowly bleed the remainder into the low side using the low side valve. Close the coupler on the high side and open the high side valve on the manifold. Bleed everything back into the low side until the pressures equalize. Then you can close the low side coupler and disconnect.
A _lot_ of dry ice is much cheaper than a credible recovery machine. Most recovery machines have orings that struggle with hydrocarbons, so it's a much more cost effective way to do it. I bought a cheap Chinese recovery machine (still $800), sealed the electrics, replaced all the seals with viton and am good to go. I could buy a lot of dry ice for that.
