For floor time, cover places they're likely to hide in with old towels. provide houses for them, lay trails of herbs between them. Spend time sat next to the cage with herbs just chatting to them, or take to doing something quiet next to the cage. I do homework sat next to them, sometimes i watch Dvds near them (although not too loudly, they do desensitise, but loud noises still scare them). Every time you wander past their cage, drop a treat off for them (mine like basil, parsley and mint best) talk to them as you do it, tell them what you're doing, and then leave. Literally poke it through the bars, tell them what it is, if they can see you doing it all the better, then go.
They'll start looking for you because you bring treats. It's cupboard love
But they do need floor time. And more than one place to hide. they're much more secure moving between hiding places.