Still on the possibly inhibited airflow subject: Make sure the condenser isn't packed with bugs/road debris. The best fan in the world won't help if it's clogged. It should be cleaned anyway even if it's not the problem. Check and clean your engine coolant radiator while you're at it, too.
I don't see anything wrong with the DIY recharge cans as a diagnostics/temporary fix. I highly advise against the ones that have leak sealers in them, though. I wouldn't trust a bunch of foreign chemicals designed to clog holes circulating through what should be a sealed system. Chances are they won't work or at least won't be a permanent fix and then you'd have these extra chemicals (contaminants) in all the lines, the compressor, the cores, etc. that will need to be cleaned out once the system is opened up for repair.
Although the gauges on the DIY cans are sure to be inaccurate, they're probably close enough. You can get an accurate charge by performing some fancy calculations and accurate temperature measuring. But, I wouldn't worry with all that cuz it's just a temporary fix that will eventually require professional equipment and replacement parts. I recharged my S10 A/C countless times by injecting it until the compressor's cycle times seemed about normal and the Temp Probe's display I had propped up on the dash read low-40s.
