As a general development strategy for "found film", I went with a suggestion I read online somewhere to use a low fog developer at high concentration, but low temperature; which led me to HC-110 at dilution A and a temperature which I try to get down to around 40F. To determine the best development time, I have always performed a clip test similar to what is described
here. So far with about a dozen developments under my belt (including three rolls of Verichrome Pan), I have to say that I have been rather pleased with the results.
When it comes to the clip test my method is actually a bit more complicated than described on that site, and frankly is rather tedious. But the interesting thing is that the resulting times are pretty much right in line with the original Kodak recommendations! At least once the dilution and temperature are factored in. For Verichrome Pan, Kodak recommended a time of 6 minutes in HC-110(B) at 65F, which according to my calculation works out to about 9-1/4 minutes at dilution A and 40F. For comparison, one of my clip tests resulted in a time of about 9-1/2 minutes - so pretty much the same! I will have to do more tests to see if the trend holds, but so far I am not finding it necessary to add extra development time as is sometimes recommended.
Here are a couple samples (first was from a Kodak Monitor, second from an Imperial Reflex 620):
