After a while of looking into my options I found a product by Critical Mass Games called "MaskFX". They are precut sheets of masking, in a digital pattern. They even make a "15mm" sheet, which I thought would be perfect for Infantry figures.
The company is based out of England, though their shipping was very fast and the website was easy to order through as a US customer. The website isn't really clear on how much masking is on each sheet, or how much to buy, so I picked up two "28mm" sized sheets and two "15mm" sized sheets. My logic was I could the smaller scale sheets for my infantry and the larger sized masking for my vehicles and larger suits. My first disappointment was when the masking sheets arrived. The two "scales" are the exact same size of masking, only the "28mm" sheet holds more masking. Not a big deal, but just a bit of a let down.
I decided to try the masking out on some Crisis Suits and a Suit Commander. I used three different greys from GW for this process. I used Administratum Grey as the base coat. Put down some masking, and then Dawnstone. This was where I started having my first issues. The MaskFX adhesive isn't that great, so the masking has a tendency to pull away from the model if it's wrapped around anything, or not on a flat surface. While it is good that the masking isn't too strong so it doesn't pull paint off it doesn't do a great job of staying put. After my second spray I did some more masking and sprayed the models with Mechanicus Standard Grey, my final coat. This would give me three different colors on the models. For pulling the masking off I highly recommend using some tweezers. The masking is small and hard to pull with just a hobby knife.
Below are the results I got. Unfortunately, since the masking doesn't stay down as well as it should, some of the masking is not as clean as you may want. Since I am doing "dirty" camo, and will go back and put chips in, it will look okay for me. If you are picking about it, you may want to avoid using this product.
After completing the suits and being relatively happy, except for the "not sticking well" problem, I decided to move on to my infantry. Since the infantry (fire warriors and pathfinders) are smaller then the suits I decided to do only two colors, Administratum Grey masked off and sprayed with Mechanicus Standard Grey. This would have the most "striking: pattern, save me a masking step, and really not lose much.
Since I was only doing one masking I decided to do more masking so the camo would be more pronounced. Since the masking has issue on curves and "non-flat" areas I also decided to do every helmet, shoulder pad, and gun heavily. I think this will show up on the table top and you won't notice the legs and torso's don't have much masking on them.
It takes a long time to mask, about two and a half hours to do 46 infantry models. I may just be slow though. What this does mean is that by the time you are ready to spray a lot of the masking would peel up and not be sticking to the model. You can see below that before I sprayed each model, I had to press down on the masking to get it back in place. I was reasonably successful in getting the masking where I wanted.
I was reasonably successful in getting masking back to where it needed to be before spraying, though once again, some of the masking is not as clean as I would have liked. Since I don't mind a dirtier look to the camo, it is not the end of the world, though it is a bit frustrating the product doesn't work as well as I think it should. The Infantry had more issues then the Crisis suits, you can clearly see in the below picture how many of the lines were not clean between the colors.
The models so far I've done using the MaskFX digital camouflage masking.
Overall I'd give the product a B+. I am going to use it to finish this army, I do really like the look it can provide. I wish the tackiness of the masking was about 20% more so it would stick once you lay it down. It is a balancing act with any masking material as you don't want too much adhesive or you start to pull the paint off when you pull the masking, this just needs a touch more. I also would hope the website would get updated to clearly define a bit better what you are getting when you buy it.