I use IEM's on every gig I possibly can, even if I'm the only one in the band doing it. I do it the same way others here have mentioned: Monitor mix (without guitar) into transmitter input, headphone out from Kemper into the second input.It's been that way for me even pre-Kemper. So we're talking...I dunno, 2-300 dates? Tons of vastly different settings and situations. Would love to offer some personal advice on the subject, of course YMMV:
-It's going to feel super weird and isolating at first. Absolutely. You will get used to it though and learn to work around it/live with it though. I hated it the first 3 or 4 months. And then I played another gig on a wedge and realized that I never wanted to be without them if possible. Haha.
-I've loaded my iPad and phone with every proprietary digital board app that I can find, and immediately download new ones when they pop up. SO MANY venues are starting to make the move to digital boards now that the tech is getting so much cheaper, and a lot of them go the full route with routers so they can mix from wherever with an iPad. Half the time these days I can just show up with my iPad and get the WiFi info, thus allowing me to access their board wirelessly and run my own mix.
-As you do more gigs with them, you'll start to get a really good idea of how much you need of each instrument. At this point, even if FoH is responsible for running my mix and we're running super low on time, I can get things at least 90% of the way there during line check (I just have him dial in my levels while he's getting gain on each line).
-Due to limitations with the number of aux sends from most boards, it's incredibly rare that I get a stereo mix. You can still get really good mixes in Mono though if you know what you're doing. Primarily: be REALLY careful with low end, unless you have really nice ears with tons of subs in them. Kick/Bass/Bass heavy synths will take up a ton of space in your mix and totally mask everything else if you accidentally dial them up too hot. I always start super low and then have the sound guy bring them up if I really need more. Beyond that, make sure you only put things that you actually need into your mix (at least at first). For example, I have the lead vocals running very low most of the time, since I essentially only need them for certain cues and knowing which verse we're on. If the band has an acoustic player/percussion/mandolin/other auxiliary stuff, I rarely put them in my mix at all. Start with the hyper-necessary things and gently add the rest from there.
-Lastly, a fun little trick for dual input transmitters: When I can't get an IEM mix for whatever reason (not enough sends, not everything getting sent to the board, weird snake location, etc etc), I typically bring a good 'ol 57 and an XLR and plug that straight into the input that my mix would normally go in. Then I take the 57 and stick it somewhere on stage pointed away from the drums (or sometimes, if I have a wedge, I'll literally "mic" my wedge). At that point, I'm literally getting an approximation of what I'd be hearing on stage, only at a much safer volume and with a bonus "more me" control. I've done this at maybe 20 gigs and it's always surprised me how well it works. Haha.