I've carried 2 guns a few times. I had a 3" 65 IWB on my right hip and a 642 in my front left pocket, with a couple of speed strips with .38 ammo in them so I could reload either gun. I found it difficult because I'm one of those guys that carries a bunch of stuff in my pockets, so re-organizing everything was a challenge.

FWIW, I think the best route is to have the same manual-of-arms for both guns. I think it's also a good idea to have one of them accessible to your offhand side, i.e., if you're right-handed and carry your primary gun on your right side then your BUG should, ideally, be accessible to your left hand.

I personally like the idea of carrying two J-frames. Since I now have two 642s I may do some experimenting with it. There are some options. As I mentioned before, I've carried with one gun on my strong-side hip and my BUG on my offhand-side in my front pocket. Some other combinations I've considered, but haven't tried, include: strong-side hip and offhand-side ankle; strong-side hip and upside-down shoulder holster; offhand-side cross-draw and strong-side front pocket (this is actually the one I like the best, but as I've said, I haven't tried it, so it may suck in actual practice...*shrug*); both front pockets; and one on each hip (offhand-side either standard draw or cross-draw). My biggest concern is when my primary gun is not on my right hip, as that's the way I've been trained and have been practicing for years; I'm afraid if I did have to respond with deadly force I might go to my right hip out of habit/programming and find my gun isn't there because it's somewhere else.

However, I don't see carrying a BUG as being critically important. I think carrying a good trauma kit should have a higher priority than a BUG.