Leash walking

I know I've asked this before but I can't seem to get it right.

Here's the short version of my problem: I'd like to be able to walk my dogs without them pulling all over the place, pulling me over or overall just making walking with them miserable. I'd like the walk to be relaxing and enjoyable for all of us.

Here's the long version:
When I'm training my dogs, at home, out and about or at the training center, they are wonderful. Both of them are top of the class and in class/training sessions they heel perfectly or walk on loose leash perfectly. I train them separately and we work everywhere: backyard, home depot, our normal walking route etc and I can get perfect compliance. The thing is, and maybe this is where I'm wrong, I'd like to just take them for a walk without having to be in "training mode" the whole time. I don't need them to heel next to me the whole time, I want them to be allowed to do some sniffing and I want to be able to disengage a little bit or talk to my husband while we walk but I need them to walk on a loose leash. It's miserable to walk them right now because I either have to be 100% into training them or they are pulling all over the place.

I brought this up with Rio's puppy trainer and he basically told me to do what is in MSP, which we've been doing all along. I've gone back and am re-working everything. We're back to starting in a quiet, distraction free area and I'll build up to distractions and then to distance.

I must be doing something wrong though to not be able to get this right. I see lots of people walking with well behaved dogs and I'm sure that some of them don't do the same level of training I do, so what is it that I'm doing wrong? Will I ever be able to just enjoy a walk with my dogs, or will it always be a chore?

BTW: Both dogs are walked separately at this time, one day (but this is probably dreaming) I'd like to be able to walk them together