In the last few years, inexpensive multi-meters with a capacitance test function have come on the market (they used to be quite expensive). Other than one of these meters, it's just trial and error. I've read of guys who would go to their FLAPS and by 5 or 6 and just try 'em. (My partner in the condenser project always had an expensive meter.)
The only "shade tree" test I know of involves an analog multi-meter. Here's a "YouTube" video showing how to do it :
https://www.youtube.com/watch?v=HF2uI7HVyWE