Sadly, it's a PITA. There is NO simple/easy solution - unless the FOH guy is your own sound guy for every gig.
This is why many bands have moved to their own IEM monitor systems. All 5 I've played in this year have their own system.
You get a small footprint 16-ch digital mixer (X32R, Ui24R, DL16S, XR18, etc..), a 16-ch splitter snake housed in a rack and a router. DON'T use the built-in Wifi on these mixer.. they're basically worthless.
That rack can also contain any wireless transmitters for those who use them. If not, an XLR cable to the band members wireless works just as well. For wired monitoring there are number of solutions with a Rolls PM or Behringer P2 being commonly used.
The splitter snake has a 2-fold use.
It's there to a) send a feed (split) to the House if they don't have one to give you or b) get a feed from the House.
NOTE: The short leg of the splitter snake is permanently connected to your mixer.
If no house feed, all mics go into YOUR splitter snake "box", with one side (leg) going to your mixer and the other to the House inputs.
If the House has a feed, you simply connect their feeds to the splitter snake box.
This works best if you are doing your own gigs.. meaning you're not playing where backline is provided, etc.
The advantage is you get to control your own IEM mix via tablet or phone by connecting to the router to which the mixer is connected. No trying to get FOH attention and have them interpret what you need more or less of in your mix.
For every gig, you can save the settings (Scene) on the mixer and recall them next time you are at that venue.
This significantly reduces soundcheck time as your IEM settings will be the same as they were when you were last there - and you only need minor adjustments.
I recommend practicing with IEM (headphones) to get used to the isolation (after using wedges/amps) and ONLY put what you need to hear into your IEM mix. It's very difficult to get a CD-quality IEM mix with a mono feed as there's little separation, no panning and EVERYTHING is centered. It can get cluttered pretty quickly and end up being a mushy mess where you can't hear what you need to do your job.
PS: Read the doc in my sig if you have questions on using wireless in a band.