Leaving prints in Dektol, lower concentration (I think- from memory here and I might have it backwards, and it was a while ago but at least 1:3) for longer periods can raise print contrast. The down side to this technique is to wait 4' for each print, or get a tray warmer and run the bath at something around 24C for 2:30.
Longer development lets subtle greys come to life that don't surface as quickly. The other option is to add pottasium bromide, which slows down development, and will need more exposure as well, but does increase print contrast.