I use calgon (could not find RLR locally) and have a HE FL. I think with RLR you use the recommended amount, but with calgon you use 1/2. I start with clean diapers, then add the calgon to the detergent spot and wash/rinse on hot. Unfortunately my machine only has a hot wash/cold rinse option, so I do that complete cycle as many times as needed until I no longer see bubbles during the hot wash cycles. I will probably be doing it on Sunday as I just switched to Tide and I seem to be using too much detergent (lots of bubbles after three whole cycles!). HTH!
Re: What do I need to know about using RLR?