I assume the yard they're running in is enclosed? If so, I'd just coordinate their dinner time with their cage time. Eventually, you'll just have to open the cage and they'll come running to hop in! (Bunnies are HIGHLY motivated by food.
)
However, if you still want to train them to use a harness and leash, you need todo itSLOWLY. I think of it like training a horse to take a saddle. You don't just pop the saddle on, mount up and expect the horse to follow your leg and hand commands. You're more likely to get bucked off! Instead, most horse trainers start very slow. The rub the horse with the saddle pad, then they eventually progress to laying the pad briefly across the horse's back, then finally leaving it there, then adding the saddle, etc. This process takes days or even weeks and it can be months before a rider even attempts to get up on the horse's back.
So, the same goes for bunny harness training. You need to get the bunny used to the harness. Let him see it, sniff it, taste it, etc. Then you can progress to putting it on him and leaving him in it for a few minutes (inside his cage, of course). Then, once he's okay with that. Add the leash and let him drag it around inside your house for a bit. Let him see it's no threat. Just go EXTREMELY slow (especially because your bunnies had a bad experience with it!).
As for putting pressure on the leash, again, that's something that you develop in time. While Gus doesn't exactly come when you tug the leash (he's more likely to look at you and then hop the other way...
), he certainly doesn't spazz out when you tug on it and in several instances, I've been very glad that I've been able to put the brakes on him before he hopped out in front of a car or ducked under a fence!
Most importantly, the rabbit has to know the leash isn't a threat and slowly get him used to the feeling of it andhe'll eventually become fine with it.
Hope that helps!
Rue