I think for some folks it’s a real cognitive challenge to willingly ignore useful information.
I know it was for me; I needed a das keyboard to make the learn-to-type “metagame” have sufficiently imperfect information to become “playable” enough for me to stick with it.
I’ll never forget one kid who didn’t bring in a box used his gym uniform shirt over his hands and tried to pass it off as the same thing. The teacher didn’t buy it. But sure enough the next year all of the keyboards had little cloth hand covers velcroed onto the back and the shoebox project was no more.
If I remind myself not to look then I can touch type just fine because I've been using keyboards for like 15 years..But I still find myself looking down as I type multiple times a day out of habit. I've often wondered if getting blank keycaps would help with this problem but have never made the jump (mainly due to cost). Someday!
Even just writing this comment I found myself looking at the keyboard instead of the screen..It's a really bad habit because it is almost like a small context switch in terms of switching back to what I should be looking at.
I'm not sure this will work for all types of keyboards, so make sure it's one you're willing to sacrifice... but that's a lot cheaper than the fancy blank ones and possibly cheaper than a can of spray paint. Also, it's probably not going to work very well with anything ergonomic.
I'm not sure I've seen a keyboard with F and K keys with bumps because that would be the index finger on the left hand and the middle finger on the right hand. Usually the bumps are both under the same finger (F and J or D and K).