I have drill bit dispenser cabinets, so about a dozen or better of each size in fractions, letter, and number. So if I need a smaller plug weld to accommodate a narrow flange, or other sizes as needed, I simply drill the size plug weld hole desired and make a cleanout bit to fit that size as shown in the video. Since they are flat, It’s only cleaning paint from the adjacent panel, so they just about last forever. As to the 135* drill bit, IMO a drill bit of whatever taper you’d like is going to cut into the next layer, no if’s ands or buts. Since I run my welder on the hot side, that isn’t an option for me as it would blow through. End mills are about 3 to 5 times the cost of drill bits, unless you have a good source.. But use whatever means works for you. I was just showing this as an option to clean for plug welds while leaving as much rust protection as possible.