I believe your 600D has a 720/60p option...it's not great but if you keep the camera close to your subject you shouldn't notice the difference in resolution too much. Other than that, you can use frame blending in your NLE or the Twixtor plug-in for PP, FCPX, AE, etc. Try not to move the camera too much if you're going to use software to fake the slow motion. Twixtor specifically will have a far easier time doing its job if the only thing in the shot that's moving is the subject.