Invasion stripes were almost all hand painted. Depending on who painted it, how much time they had to paint the stripes, etc., depended on how nicely they were done. There were directives handed out as to how to paint the stripes, but they were temporary, so you'll find that no two aircraft are alike in positioning or quality.
I've seen C-47s with stripes that looked like a 4-year-old did them with a mop.
Remember, too, that most aircraft painted those stripes out, or stripped them altogether, by August/Sept. of 1944. Very few aircraft carried them into 1945.
This was a critical time in the USAAF. Aircraft were going from Olive Drab to Natural Metal in an effort to improve performance. Stripping the paint off an aircraft and polishing it could increase the speed by several mph in some cases. By mid-1944, especially over France and the low Countries, the Allies had air superiority, so camouflage wasn't a necessity. On the long range escorts, camouflage at 30K is pointless, and again, if they could reduce the weight of the aircraft by a few pounds, that's extra range, speed, fuel, or ammo that they could carry.
