The "kindest" way I've seen it taught was to basically use a hobble on one foot ,say horse's left front, with a lead attached to it. (the hobble buckles and never gets tighter so it's not causing any discomfort) then the lead is pulled up and dallied one time around the saddle horn. Now what you would do with a horse that TRUSTS you is ask or cue for "back". The horse will lean back and eventually lay down. Once the hose is down you un-dally the lead of course. It must be done in a controlled environment and a soft spot to lay in...also this can be very hard on your saddle...I suggest using your hubby's
There really is TOO much to explain it properly on here. What I wrote above is really a condenced "nutshell" form of the method. Because you are also wanting to teach the cue to do this while you are using the leads. I saw it done for an older rancher gentleman that had had a stroke and lost the use of his arm and some in his leg, yet he still ranched. So the horse was taught to lay down so this man could mount and work. I'll try to find a link for you that may explain it better.