I work better alone too. Been working that way for 25 years. I don't usually know what to have a helper do so often they just give me a third hand here and there. Most of the time I use masking tape for that. Hard to justify paying a guy to emulate a piece of masking tape.
Never thought of using a pattern. Sounds like a feasible idea. What I usually do is scale up a picture of the vehicle actual size and measure at various points. I'll print that out as my blueprint and line the vinyl up according to my measurements. Still often needs a little tweaking but works for me.
I may try a pattern on a job in the future as it's not a bad idea.
btw.. good job on both vehicles.