Aside of having a crimp making tool, it will be difficult. I have hand pliers made for that purpose. The crimps must be made deeper to shrink the diameter of the pipe. I don't know if you can twist each crimp a little with heavy duty needle nose pliers and be effective. The other way would be to use a cold chisel and a vise. With the jaws slightly open, place the crip end over the end of the vise jaws and use the cold chisel and hammer to tap each crimp bottom groove.