I was in your situation last year.
There is no paid information I could find on Champ Coach or Coaches Choice. There is an annual clinic - mentioned above. Sometimes you can buy the clinic videos from past. They are helpful.
There is a book on 6 man called or known as the "Green book" that has a lot of information. I can't find it and can't remember the name. Its green I think. I remember seeing the cover. Someone here probably knows the name - I lost the name.
Glazier clinic online does has some six man. I found it useful.
Conditioning of players is key - to me the game seemed like high school spread Run left, pass right, make defense run.
Tackling in open space is key. A defense that bends but doesn't break is great. Turnovers are huge since it can be difficult to stop offense.
Special teams for me was huge since XP kicks were two points in my league and its hard to do - operation time is less than 11man high school xp but I was fortunate with smart kids and three snappers with OP time of 1.35 in middle school.
Glazier Online
Worldcat.org for a book search then buy it on amazon
TX Six man clinics - really good.
Get a coach to talk to you that you don't play for advice
Learn to tackle in space
Learn to stalk block
Atavas Tackling
https://highandtight.com/pages/comprehensive-training-system
This is from Coach Murray. No talking here but if you study the video and read what he writes you will be way ahead.EXCELLENT
Cone drills 1
WR Catch Stationary drills 2
WR Catch Moving 3
WR Route drills 4
WR Release drills 5
WR Contact drills 6
WR Blocking Drills 7