my best luck has occurred when I have seen some volume. You have to keep an eye on this one because it will go for days/weeks with little or no volume and then one day out of the blue there will be some activity.
Radium - I've basically accumulated by buying 1/4 to 1/3 of my shares at the lowest ask I can find in the CT's or preferreds while keeping lower GTC bids in. Occasionally then they will partially fill my lower bid.
You will have to call your broker to find out what the real bid/ask is. They rarely post the correct numbers which, IMO is one way to keep these from trading. The MM's can post what ever numbers they want real or otherwise.