I use both a Jewel and a Viking longarm for charity quilts 2 full days a month. After a little prep work it takes me 5 minutes to load a quilt. The quilt is basted with #6 stitch through all 3 layers at the top, with the backing extending about 2 inches above the stitch line. Then a top and bottom header is sewn to the backing fabric, again using a long running stitch to make it easier to tear them off when finished. Starting from the middle line, the headers are velcroed to the rail leaders and the backing tightened. The other two quilt layers float free below the top stitching. There are two elastic clamps/pulls on each side to help keep some tension on the backing. Between the weight of the hanging layers, my tummy, and my hand I can control how much tension is on the quilt.
None of the quilts wider than 60 inches so I don't know of difficulties relevant to a wider quilt. I haven't had any need to put the batts or the tops on the rollers due to the smaller sizes of the quilts.