I bought the blue foam sleeve for the H.O.T. Magnum, type "U" for my Protege with a 901. IMO it far superior to the PTB method in terms of effectiveness and prep time.
I like vaping, but I am always looking for a way to make it easier and even more inexpensive. Here is a neat trick I tried with the blue foam that worked out well.
I cut the seam off of the sleeve using the paper cutter at my office. Then I unfolded it, slid it back into the cutter, measured 5/8", and pulled down the handle. Smooth as a mayonaise sandwich. Repeated it three more times. Now I just have to experiment with the length to try to find what works best, and I have three long strips I can easily cut. Fast and simple.
One more thing, this foam method is incredibly inexpensive. I paid $8 for three sleeves @ Petsmart. Doing some back of the envelope calculations, and assuming you use the the foam material for three days of vapin' and then toss, your cartridge material will end up costing you about $.0075 per day or $2.73 per year.