I type on a keyboard with only my two middle fingers. This was likely more efficient for my tiny hands at five years old than methods urged by the typing CD-ROMs we had at that time. However as I grew more proportional to a standard keyboard, this early typing style has persisted. I have no idea where to even begin changing this now as it’s been deeply ingrained by decades of habit. Anybody have experience with changing a muscle memory based habit like this?
Since you at least know the layout. Typing of the Dead can be fun for forcing you to start using more fingers as things come at you. I needed to force myself to get better in order to make sure I could pass a timed typing speed and accuracy test for a data entry job. Played it a little every night for at least a week before my interview. I was still kind of slow, but was much more accurate. Which got me into a position that corrected or found missing information from the main data entry folks. If arcade zombie games aren’t your thing, there are some other good games mentioned in the other comments.
Glyphica has a demo on Steam that’s good enough for you to get some practice in for free. Typing tower defense.