I think Remus has perfected the art of doing everything one handed, when he remembers. But he has a habit of forgetting there's anything in his other hand and just dropping his crutch/cane on the ground.
He's also perfected the little kick to retrieve it off the ground without bending over.
You will never catch him using both of his crutches because he panics and doesn't know what to do when he needs to hold something.
(For Christmas one year Sirius got him a set of crutches that go all around the forearm (among other things) and Remus who's had to buy his own medical equipment and knows how expensive it is demanded the receipt for a WEEK so he could return them. He didn't use them for two because everytime he looked at them he'd feel overwhelmed with love and cry)