The first thing to look for in a crack pipe is a nice cylindrical base. Keep in mind that If the flow of crack smoke up the pipe is obstructed in any way, you're just wasting your crack.
You misunderstood entirely.
Depending on the material, the pipe should be ground into powder or fine chips before you roll it (a binding agent might be needed. Cyanoacrylate works fine). Some materials are easier to grind than others, but I'd recommend breaking even the softest wood pipes into smaller bits before tossing them into the blender. Obviously, metal pipes are hard to powderize and even harder to light and as such should be avoided. Don't bother with filters; if you want to smoke a pipe, you'd better smoke the whole thing.