FP4 is 3 times slower than HP5 film(generally). What this means is it will take 3 times more light to expose... I would make sure you always have your flash turned on with the holga and try to shoot only in daylight. Or not farther away than 6 feet from your subject.
As for development times, the will vary from film to film. We use ID11 film developer which is marked on the chart closest to the sink. All the film developers are listed on the vertical part of the chart. The films are on the top horizontal.
FP4 i believe has 3 potential speeds, so you'll have to check to see which one you're using. The development times shouldn't change from 35 to 120, so you can develop both in the same tank, as long as they are the same film, or the same development times.
you will dilute your film developer (1 part water to 1 part developer)
if the ISO (film speed) is 50 you will develop for 8 min.
" 125 " 11 min.
" 200 " 15 min.
check your film to see what ISO it is, and then double check the chart as i'm doing this from memory.
If you have any concerns give me a call or let me know when you're going to process and i can come down and be there in case you need a hand.
wet, dirty and dangerous.