A Rope mostly. Surprised no one mentioned how. I tie a loop big enough to fit over the cam, put the loop under the cam and flip it over the cam. When you pull the rope it can't come undone and when you reach the top all it takes is to flip the loop of the cam and the ropes free. No fumbling around with knots and limited scent.

I would suggest using a bolin knot on just about everything. It won't come a part unless you want it to. It will always come undone quickly.