Exposure times are usually along the lines of 13 minutes. The drop of 2%Potassium Dichromate makes the exposure longer than it would be without it but gives it a nice contrast boost.
Exposure is by BLB flourescent spirals - 60 w equivalent. I have six of them. They are about 3 inches from the paper, set close together. The exposure is even and consistant.
I started double coating because I wasn't getting good density in the shadows. One coat for me looks washed out but I understand that everyone's process is slightly different - depending on, well, every other variable.