Christopher, start with processing 6 sheets until you can do it in your sleep. Btw, start with practicing loading blank sheets/duds until you feel that you are very confident with that. The CombiPlan is a good device, but practice is indeed needed.
Also, when you have less than 6 sheets to process, load the empty slots with blanks, so that the chemicals circulate in the same way.

When you are past confident with 6 sheets (i.e. maybe 20 times maybe 100... Yes, I'm serious.) you can start with 12 sheets. I'm not sure if some kind of mesh will help, but that is your choice. Even with a piece of mesh (which means something extra to fiddle around with in the dark), there is a good possiblity that there will be leftovers from the anti-halation backing.
Now, it was a bit of revelation to me to read up on the BTZS tubes some 10-15 years ago. I'm thinking about the bit where they take simply take off the lid and drop the now lidless tube into a bowl with stop bath, where they are collected until you've done with all the tubes. Only then you continue with the fixing part.
So what was the revelation regarding the CombiPlan? Well, one of the downsides with the CombiPlan is that it takes ages to drain and refill. So I got me a couple of jars which were somewhat similar in shape to the CombiPlan tank. I filled those with stop-bath and fixer and had a go with some less important pictures. After my e.g. 10 minutes of developing I switched to the red darkroom light and simply ripped the lid from the CombiPlan and lifted the holder over to the stop-bath container. After a minute I continued with the fixer. Indeed it worked, even though I was somewhat stunned. There was no sign of light damage what so ever.
I later skipped the third container and took the films out of the holder and into an ordinary 5x7" tray with fixer.
I've been using this procedure for developing sheet film for 3-4 years without any traces of light damage. Nor have I had any unpleasant surprises with any 35mm or 120 film when I've done similar things. (Nowadays I use a Jobo CPP2 with Expert drums.)
Anyhow, if you feel that this is a way to go, you will not have any problems with clearing the backing of the films.

//Björn