It happens to the best.
The oversize bushings and tap are easy to work.
Basically, you are "chasing" the threads with the tap. The key is to be perpendicular to the frame. If you still feel unsure of doing it, most auto mechanics can assist. Then use loc-tite on the bushings (but not inside). After the bushings are setup (normally 24 hours is more than enough time), put the grips back on. A little oil on the screw threads may assist in avoiding this situation in the future.
I have used a large screw driver to put the bushing back in, but you have to be careful that the bushing does not get buggered up.
The oversize bushings and tap are easy to work.
Basically, you are "chasing" the threads with the tap. The key is to be perpendicular to the frame. If you still feel unsure of doing it, most auto mechanics can assist. Then use loc-tite on the bushings (but not inside). After the bushings are setup (normally 24 hours is more than enough time), put the grips back on. A little oil on the screw threads may assist in avoiding this situation in the future.
I have used a large screw driver to put the bushing back in, but you have to be careful that the bushing does not get buggered up.