I have cut some wool strips with my #8.5 cartridge. These are the needles which should be available at most craft or fabric stores. The blue plastic ones are made for kids but they work just fine for adults to use as well. It doesn't really matter which width wool strip you choose to bind your rug with as the process will be the same. However, with a more narrow cut you use it may take a wee bit longer and you would place them closer together. And it doesn't make any difference as to the length of your strip, but the longer the better as you will have fewer ends to tuck in that way. These happen to be about 31" long.
As with hooking, where you gauge your loops every two or every three holes away, it is the same with whipping your edge. Yet, the previously pulled loops just might provide the rhythm you need.
As you can see from the photo below, I have tucked the first end entering under the black thread, and now I will double back, covering that edge with my whipping. You could also tuck it inside the rolled up backing (foundation).
I usually enter my needle in thru the back of the rug, that way I can be sure that the strips are entering in the same row all the way down the line. You could enter thru the front but to me it takes a little more effort to see if I am keeping in a straight line by having to push the roll of backing to view it when it is so easily seen from the back. But I also check the front to be sure my needle hasn't caught a loop. So in reality I am looking at both the front and back as I go along.
And then when I come to the end of that strip, you can either tuck it under the previously whipped stitches or tuck it under the rolled backing.
This is only one way to bind a rug. As I do other projects I will show you other ways of binding. Good luck on your project and feel free to write me with questions or ask us on Rughookers group.