Not a lot out there in terms of instructional video's at least specific to airguns. More so with benchrest in general.
First thing you will have to figure out is what is available for you to compete in, in your local area. 25m and 50y are governed and most places that have airgun benchrest will offer these. Longer distances are ungovered at this point, so if you are mostly interested in competing at 75y, 100m or further it will be club/event specific.
For the 25m/50y game you can use 0.177cal to 0.22cal rifles. There are two manufactures that make dedicated benchrest guns that consistently show up at the top of the results, ThomasAir and RAW. While any air rifle that will sit still on a rest will get you started, sooner or later you will just looking for more precise tools.
My best advice would be to find a nearby club and go to their matches. See if someone will let you shoot their rig for a match or two before you start investing money. IMHO you will save money in the long run if you buy high quality gear to start with and frankly you want to be sure this is something you want to do before you drop thousands and thousands of dollars on gear.