The key to effective draw is wrist snap and acceleration! You must learn to "snap" your wrist/cue tip through the lower half of the cue ball at increasing speed and at the right moment. All that stuff about follow through is kind of a misnomer when it comes to specific stroke or power shots. You can follow through whitey all night long and still not get adequate draw! I'm sure you can relate! Therefore wrist snap, acceleration, and timing is the secret.
Unless you are naturally big, strong, or have arms with enough mass to muscle-draw the cue ball, small - normal players must rely on wrist action. I've long had difficulty with draw and the mechanics of wrist snap. While the words seem self explanatory, no one properly defined the term until I read Johnny Holiday's book: The Encyclopedia of Pocket Billiards. From it I got a short definition of draw and the mechanics of the stroke. He calls it a "snap-back" stroke. What I understand from his explanation is as your wrist snaps forward into the base of the cue ball, you should quickly pull back or yank your hand back at the wrist. This gets you to stab quickly into and through the cue ball imparting a huge amount back spin (if desired). You'd think doing this would hinder the action of the stroke, but it forces you to ad extra speed into the ball much like a firing engine piston.
The Monk also used the words "snap-back" stroke - verbatim - in his popular book: Point The Way. In fact, he used many of Johnny Holiday's ideas and published them in Point The Way!!! I'm not bashing The Monk, but I didn't see a writing credit or bibliography with Johnny Holiday's name on it!!! What's up with that?!!!
I was still a little confused after reading Johnny's section on draw (what the heck is a snap-back stroke?!!!). However, after practicing what I read - at the pool hall - for 20 - 30 minutes I finally got it!!!
To describe more of the mechanics... visualize holding an 18" Bull Whip (I know there isn't such a thing!) in your hand like the butt of your cue. Now imagine "cracking" the Whip using only your wrist and you should get an idea of what wrist action truly is.
A much better more functional and fun example is to playfully snap a small wet terry towel at your girlfriend's/boyfriend's behind at the beach, etc., and you will get instant physical feedback!!!

You'll get slapped by your mate but you will also grasp the concept and mechanics behind (pun intended) a good proper wrist snap, IMO!!! Lol!!! Oh, and I won't be responsible if you snap anybody with a whip, towel, etc.l!!! Just do it at the air underhanded and you'll be fine.
You can still get adequate action without this "back" part of the snap stroke. I think the idea of "back" serves as both a mental and physical cue and aids you getting extra wrist action into that cue ball. For the first time in over a decade I finally know what a wrist snap is!!! Now when I shoot 5'+ draw shots the cue ball contacts the object ball, pauses for a split second (fairly new simonis 860, red circle cue ball) and zips back with amazing speed!!! I've never intentionally been able to do that, ever!!! The action is incredible and I get the same results on worn, dirtly, old cloth! Of course, since timing is also essential you have to be pretty warmed up to do it right. At least in the beginning. No, I don't use a predator shaft either! That'd be akin to cheating!!!
The next thing you have to practice is speed control so you don't run over run your mark! The cue ball really likes to run back quickly with this type of stroke, and you have to gauge the exact amount of wrist action to use.
Sorry for the long winded reply!! It's the best I could do! Hope this helped! "Stick" with it and I'm sure you will get the hang of it eventually. It took me over 10 years!!!

Remember to practice hard, but keep things in perspective and have fun!!! Few of us can draw like Mike Massey, even with proper technique!!!!
Sincerely,
F8it