I have shortened mine as well. This is how I do it. You sound like you went over the top with paint for an antenna, but Im sure it looks good.
Put antenna in a vice and take pliers and pull off the ball.
Make sure ball doesn't hit ground or they are very hard to find.
Take cutoff wheel, grinder or hack saw and cut to desired length.
If the ball won't fit back on (usually doesn't) Take a bench grinder or similar to the end and make it thinner so the ball fits.
Superglue Ball to Antenna
Let Superglue Dry.
Take Black Spray paint and shoot the whole thing
Let dry and reinstall. its easy to do.