Here is a nice short instructional video for those interested in how to graft cacti seedlings fast (https://www.youtube.com/watch?v=U2Q_HKxVQP4&feature=youtu.be).
Click on the word fast if your lost. I'm using parafilm as my wrap in this video.
And for those that like to see grafts in picture format... Not exactly the same, but definitely the same method....