At one time I used 12' long 2x10's, that worked
I also have used some HDPE plastic sheets I had, about 5' x 1' x 3/16". I placed these under the jacks and just let them slide up the driveway (plastic stays put, jacks slide on plastic)
Eventually on our trailer I was able to just raise the jacks. But if the trailer is really loaded I will still hit, so I also dump the air in my hitch and truck suspension, that gives me about 4" extra at the rear of the trailer.