Re: canvas edges
I would agree with markshirar. To paint the edges, it's easiest to do it first, using acrylics, before doing the painting itself. That way, if any creeps onto the surface, you will just paint over it. If you mess up the painted edges while doing the painting, then generally you can just touch up the edges. I find it usually takes 2 coats of a dark acrylic to cover the edges.
If the painting is already done, as I presume is the case here, you can still paint the edges with acrylics, but have a cloth at the ready and be vigilant -- to wipe off any that gets onto the surface since acrylic dries so fast. And I agree that painted edges in a floater frame really looks great, especially with modern/abstract paintings.