The tumblers always drag on the key, so I don't think your marks-a-lot approach is going to work. However, these locks are very easy to pick, so my suggestion would be to Google for one of the many lock picking videos and try it yourself. While the internal construction is somewhat different than a normal "pin and tumbler" lock, the picking procedure is the same.
Basically you need two tools, one to apply a bit of rotational force on the cylinder (but just a bit), and the other to reach into the lock and lift each pin in turn until that pin is unlocked. When they are all unlocked, the cylinder will turn. Here's one site with a video:
https://home.howstuffworks.com/home-improvement/household-safety/security/lock-picking2.htm
Or, have a locksmith come and do it for you. If you have a AAA card, I believe they will cover the locksmith at no charge.
The other route, of course, is to plan on replacing the cardboard compartment (which probably needs it anyway, they don't hold up very well over time) and just cut/tear a hole in the bottom of it. Then you can reach inside and undo the hex-head bolt that holds the lock lever to the cylinder; and push the door open.
PS, once it's open, it's not hard at all to disassemble the lock and cut your own key. For the glovebox lock, ISTR there is a roll pin that you have to tap out, then the cylinder pulls out. The tumblers are theoretically captive in the cylinder, so you just cut the key until it holds the tumblers level with the surface on both sides.