This should get you started. I don't use charcoal BBQ but a device similar to Weber Smokey Mountain (not a knock-off since Weber is not the original product of this type, just don't recall what was). So don't know any nuances but basic procedure is like this:
You need something to monitor the temperature of the BBQ, and inside temperature of the haunch. If there's analog meter in Weber don't trust it. Basically two digital thermometers, or one with dual probes.
Principle is, that you control the burn, temperature and smoke generation by oxygen starvation. I.e. only let enough oxygen in to keep the temperature at 100C or so. If there's too much oxygen, the apple tree bits or whatever you put in will burn and not generate smoke. Since it's not convenient to add briquettes to Weber (or any simple charcoal BBQ), you need a way to lit them one by one (few by few) not all in the beginning. One way is "snake method" where you put briquettes along the outer wall.
The haunch won't be on top of the briquettes but to the side (indirect heat). Usual practice is to put aluminium baking tray or similar to the briquette tray below the meat.
All of this is correct but maybe a bit tricky if you've not done smoking before. It can be a real faff to manage the heat in a kettle type BBQ for larger bits which needs a long time
Also smoking works best for foods which have a decent amount of fat in them as that is what tends to take up the smoke flavours (hence the classic smoked bacon, salmon and mackerel etc)
You can do it with leaner cuts but they can just dry out so not sure haunch (or most venison at all) suits hot smoking
But you can try doing it in the oven and finishing off in the smoker for an easy trial and work up from there
This is more a Texan BBQ style like you get ribs or brisket and you can find lots of "Texan style BBQ in you home oven instructions online"
3 stages
Brining: not essential but helps a lot.
Read up any recipes online for bacon or pastrami. Wet brine suits lean meats better than dry brine
Salt/sugar/spice for a few days then leave to air dry for a bit
Actual cooking
Very low oven (65-90C)
Meat covered and About 1 hour per inch of thickness but min 2 hours
Meat should be very tender
Add sticky sauces at this point if you like or half way through the oven bit
Final smoking
When it comes out of the oven have the BBQ ready
Small bed of charcoal briquettes nicely burned down all pushed to one side
BBQ preheated but not roasting hot
Cover with a bag of wood chips soaked on water for 10 mins and shook dry half on the charcoal and running into the non charcoal area (so the wood can smoulder and burn all of it slowly)
SHut the lid, seal all the vents and leave it half an hour
Not as hard as it sounds but either you need to go full science mode with thermometers and micromanaging or just accept it as an art which you'll screw up plenty and never manage to reproduce the perfect one you did the first time