With Radec or just in general? Radec's bread and butter is side square+side triangle, a good grab combo is up grab+up triangle. And if you can manage, you can try side circle+side square+up circle+up triangle (air)/side square (air). This is extremely hard though and requires some practice and aiming.
In general. I've been using Radec all day and I've rarely touched any of the other characters. I need to have a more flexible pool of characters that I know I can play as. Right now, the only one that seems to interest me is Nathan Drake. Since I've been playing Uncharted 3 for who knows how long, I'd figure that I'd be pretty good with him. I need to pick 3 more characters, then I might try going online.