You didn't say whether you used whole or pellets, but I like to use whole hops for dry hopping (no bag). They are easy to rack out from under and leave very little sediment compared to pellets.
Personally I don't think post-fermentation temperature is very critical. Tannins come from grain, not hops - though you can get a grassy flavor if dry hops are left too long. I usually leave them 5-7 days (10 max) then go to bottle.
I have used the bag trick to filter the sediment from pellets, it works but I found it to be a PITA and not necessary with whole hops.