While you could use Finesse tape and spray it the way to get a hand striped look is to get a good striping brush with some One Shot or other specific sign/striping enamel, paint your stripe, then pull the tape while the paint is still wet so the edges flow out and look like a hand pulled stripe. https://www.finessepinstriping.com/ You may want to repaint that guard to get a smoother finish or you may have bleed through regardless. V/r Shawn
To keep from bleeding under the tape, shoot on a coat of your base color AFTER you put on your masking. Let it cure, then add your stripe color. A striping brush or a Beugler striper, or even the cheap little glass bottle stripers will work better. Contrary to popular belief, striping is not hard to do.
Depends on the era, year and who painted them originally. Yes, those look like factory pins. Here's another factory version going to the end of the indents and then down. The pins never go in the indent.