Grandma Kimmit Sandwich!

I just learnt Grandma Kimmit Sandwich, from (my favorite website to learn tricks) and i would like to know one thing. the part where you pop it out from your middle finger and thumb, and land it on the non-throwhand thumb string. I can’t get that part, i am not sure if my string is too short, or my yoyo to big. so I am wondering if there is another way to do it. if there is, please comment or post a video.