I gotta jump in on this. A lot depends on you goals & present skill level. I think the year was 1961, Paul L. Failor Supervisor Predator Control Section of the PA Game Commission did a talk & demo on red fox trapping that I attended. Dirt hole, bait lure & urine or IMO the same with no hole. That's all you need to know. You can easily learn set construction from YouTube. Go make a 100 sets. Some will catch something. Learn location from this and repeat. By the time you get 100 sets on location you will have learned everything you need to know. This might take awhile. Only took me a few decades to get it.
One of the training guys can speed up your learning curve. Especially if you can find one willing to take you along on his line near where you want to trap. Over the pas 50 years I've seen dozens of the known guys do demos & I have bought a 100 or more DVD's. No secrets left to tell. Just go make sets.
When my schedule allows I will get some training, either ride with a big gun or go to a school. My goal is just to learn what I can and see how they do it on their turf. Don't know of anyone I would need to pay to do it in the BIG WOODS where I trap. Just got an idea, I'm going to contact a few guys that are good and offer them a free lunch to come and share some conservation & secrets. BTW I went to CoyotU & FTA's Trappers College.
In support of what Mercer said I have eight trail cams and need to get them out. Mine will go on holes with some lure in them.