I have a lead sled also, very easy to adjust and then it holds its zero. They're a bit pricey but worth it. If you didnt want to go with the sled, next choice for me would be shooting bags, probably caldwells.
I shoot prone off the ground when sighting in rifles. I hate typical benches and bags with a passion. In that last vapor trail video, we used an old dresser to shoot off of, just because I didn't want to have to kick holes in the wall to shoot out of.