Yes, I have some fox-calling experience. Been at it for over 15-years. So here goes..,
For starters, I am assuming that you are calling at night? In MN, we can call at night, but cannot use lights, that means that you are calling under the moon, and over snow. Use a scope, even if you are shooting a shotgun. It gives much better definition, especially if the fox responds, but stops in the shadows. And most IMPORTANT of all, you MUST use the wind. If you are an experienced coyote-caller, you know that.
Now to the foxes. The gray will be the easiest of the two for you to call. They are really fearless little critters compared to a red. To sucker them in, use an electronic call, and use a “gray-fox pup”, “gray-fox fight” or a “red fox-gray fox fight”. If they haven’t been called to death, you will certainly call them in with one of these calls. I have had them literally run right past me, full tilt, and bury their heads in the speaker. You simply cannot mess this one up.
Now to the red-fox. A completely and totally different critter than the gray. They are very cautious. “Smart as a fox” really should be stated “chicken as a fox”. And with a strong population of coyotes, the red is even less prone to run in, as he doesn’t want to become the main-course on tonights menu. But they can still be had. Again, use your electronic caller, and use high-pitched distress sounds such as rodents or birds, even baby-cottontails. You will need to be extremely cautious when and where you set up. I can almost assure you that this critter will circle downwind. So give him an easy way to do this. Set up your electronic caller about 50-yards upwind of a fenceline, in a slough, turn it on, then you hustle back to that fenceline downwind of the call. You pop him as he trots downwind of the sounds, as he comes along the fenceline. Use an old farm-road or logging road the same as a fenceline.
If you have a buddy, then double-teaming them is most effective. One guy stays at the call, the other posts downwind. Make dang sure that your buddy is a knowledgeable hunter and stays where he is supposed to. Otherwise, this is a dangerous situation if he moves, and you don’t see him.
There you have it. You should be able to kill both of these critters in a couple nights of calling, if conditions are prime.
Have fun.., and BE SAFE!!!!!