Use a very light grease on the trigger slides, and a very heavy grease on the main tuning slide. Be sure to wipe any excess grease off the exterior surfaces of the instrument. After all of the slides have been assembled, the valves need to be properly prepared. Use your fingers to forcefully rub the oil onto the entire piston surface. This rubbing action guarantees complete coverage of the valve, and helps protect Monel valves against spotting.
Some musicians blow oil through the instrument.
This is a good idea to protect the instrument interior, but does not replace proper oiling of the piston and valve casing as we described. Finally, let us say that we know that this process might sound long and arduous, but after the first time, it will be fast and easy. The rewards, however, will last a long time.