The warrants are traded like stock, but are OTC and very thinly traded. There are no contract fees, just your normal commission. I'm on the Amertrade platform and like most other people I've talked to, cannot see a bid or ask, only the price of the last trade (or a chart if I bring that up).
What I do is just put in a bid, but I've seen trades go thru for less than my bid. I called TDA once, and all they could say is that since it is OTC, when a sell order comes through, the order is called around to 3 trading desks to get a best bid. Not sure how they rotate through the various firms. Seems all I can do is keep the bid GTC and hope that eventually gets filled, though it doesn't seem fair they are filling orders at less than my bid.
Hope that helps.