Hello there.
Im in the process of learning plastic whip, however whenever I suspend the string between middle finger and thumb, and throw the string towards the yoyo, I either miss, or in the unlikely event the string catches, the yoyo flies straight back up to my hand.
Some help would be greatly appreciated, as well as any tips you have for the trick 
Thanks!
Are you using an unresponsive yoyo? If you are then you might want to check string tension, pads, and the bearing.
What yoyo are you using? It sounds like its a responsive yoyo, you need a unresponsive yoyo. And I think your ready for one.
Focus on controlling the yoyo smoothly as you pop it up instead of the natural tendency to quickly jerk the string which causes a messy slack of string (which is the reason for the unexpected bind). Think of pulling the yoyo up more instead of popping it. Also, while you are pulling the yoyo up, already have your hand and string ready in position to whip it. Practice aiming at different parts depending on which side you are over shooting. Repetition and minor adjustments are ultimately the key to consistency!
Mainly, like other posters I wonder about the yoyo’s responsiveness.
To add something, though: I also find that a nice flowing loop helps. When throwing the loop, think of throwing it “forward” instead of just down towards the yoyo. The fact that it’s anchored to your throwhand will mean that it WILL go downwards as well, so concentrating on the forward part of the throw will help with a nice big loop to wrap around the yoyo.
Yoyo is an unresponsive DM2, sorry, I should have included that! Thanks so much for the help! 
Throw a plain old sleeper. Hop the yoyo up in the air. Is the string sort of “chasing” the axle a little bit? (trying to wind up, but being all loose and not actually responding)? Your bearing could have gone a touch responsive which will cause a snaggly mess when the loop of the plastic whip hits the gap.
This is what I did:
I practiced several different motions and when I found one that worked for me, I did that.
Also, my brother was there when I was doing it had the idea of doing a trick similar to Plastic Whip. I did his trick that was the same exact motion but off of a Breakaway and hit it. That was when I realized that I could a Plastic Whip. That is also the very first time I hit it. Now I hit it quite often.
In other words, once you get it a couple of times, you get used to the motion. Once you have the motion, it’s so easy. Just do what GregP said and that helps too. Let the string do the work, don’t force it. It will come natural sooner or later.
Always remember: Make the “L” shape with your index finger and thumb, and move your wrist in a forward-downward movement. Hope that helps haha
^My daughter just learned plastic whip last week and this was her favorite tutorial as well.
Out if the dozen or so I watched it was the one that just seemed to flow the best. I don’t know why but it did. B)
How d is your kiddo? I have a 7 yr old and an almost 9 yr old trying to learn just to begin to play (we are taking baby steps).
Nice! Such a rewarding hobby especially to share something with the childrens!
The daughter that I’m talking about is 13, and the other is 10. The 10 year old picks up the Baldwin and the Loop 808 the most. The 13 year old is sporting the YYJ Classic but with full sized bearing and half silicone response as she is binding now, but still likes a little bit of help still. I recently re-learned this trick on fixed axle. Took a few knuckle smashes to get my attention. ;D
Indeed fun to share the enjoyment and watch the excitement as the kids throw a successful pass and other times watch them work on getting something right often times with their tongues hanging out lol. sorry to had you had to pick up your attention that way, but you’ll remember how to so it longer with a reminder like that.
It’s a great trick to know. It provides a very easy one hand bind.
This is all great advice! Thank you guys! Im getting closer now, only a matter of time 
Video is very good!
I actually know a pretty neat-looking 2 handed bind off the plastic whip, too!
Yeah but one hand binds are so much harder to find…
In that video I posted from Yoskills he shows a great one handed bind.