Hi and welcome back, HSG. I don't have any personal experience with venison but there are wild game marinade recipes in Steven's book Sauces Rubs and Marinades and Paul Kirk's 2 Championship Barbecue books, and I've heard and read about buttermilk marinades being used to reduce any gamey flavors.
Red wine and juniper seem to be popular marinade ingredients.
Good to see you back, HSG!
I use the wild game marinade from Sauces, Rubs and Marinades, usually. That's the one with red wine and juniper.
However, I've tried some buttermilk marinades as well and they work nicely. One of the simple marinades I've tried is as follows:
1 quart buttermilk
2 tsp salt
Juice of 1 lemon
2 tbsp chopped garlic (yes - that's right, lots of it)
A few grinds of black pepper
4-6 sprigs rosemary
I usually add a bit of thyme as well. The above marinade is a South African one for lamb but it also works really well on venison, elk, moose or any other lean big game. I normally marinate large pieces of meat overnight and smaller ones for 4-8 hours. The buttermilk also helps plump up the meat a bit and keeps it moist.