I corroborate the acrylic paint. Make sure you mix beforehand and store it if you're mixing your own color - this will ensure that every layer is consistent in color. Make sure you prime!
As for the tail - if it's plastic, dunk it in boiling water for a minute and them slice carefully. If it's haired, you're going to have to cut it shorter and push it into the body, then work your new tail in and secure it.