The Makiwara has done more to clean up my strikes than anything else. It regularly teaches me new thigns and shows me how things I thought I understood were wrong.
Well karate has a number of finger and nuckle strikes that I have only recently gotten to the point where I have added them to my stiking practice. Only problem is even soft strikes just killed my fingers. My sensei showed me a neat trick to work on my finger strikes. Basically you hang a punching target from the makiwara, then do your strikes against the pad. After a few months I was able to work up to striking the naked makiwara.
The big problem I am trying to figure out currently is my pinky finger hanging out from my hand during the strike. It does not seem to impact the stike, but I cant help thinking that having the one finger separated from my hand has the potential for it to get hung up on the harget or broken.
Now that I am regularly practicing Nukite, I can see how I am doing it wroge all over the place. Pinan Shodan for example has a Nukite strike to the throat, and I can now see I was just thrusting with a knife hand during the kata. My finger position was all wrong. So now I need to fix my Kata and my strikes.