1. Take instrument apart
Lay out a towel to place tuning slides, caps and valves upon. Position parts on towel carefully in a way that will remind you where to put them back when you are done (especially valves).
Always depress valves when removing slides from instrument to avoid air pressure build up, which can fatigue metal. Removing valves first can simplify the process.
Carefully remove all slides, clamps and valves. Handle with care one dent can result in costly repairs. If a slide or cap is frozen in place, DO NOT FORCE. Take to a qualified repair shop for removal. Remember: Brass is thin and easy to dent/bend.
2. Wash instrument/pieces
Submerse the instrument in warm soapy water. A large sink, basin or even a bathtub works well. While under water, instrument may be cleaned out with a long flexible cleaning brush. Be sure to rinse well before reassembling.
Individually clean each slide, cap and valve in warm soapy water. Use brush if available. Caution: Take special care with valves, they are very fragile. Be careful not to dent or scratch surface or edges. Rinse well.
Valves maybe disassembled but it is NOT RECOMMENDED (unless under supervision). If taken apart, give careful attention to position of felts/corks. The cork rings are brittle handle with care. New felts and corks are available at the music store. Remember, the valve itself is far easier to take apart than it is to put back together.
3. Dry instruments and parts
Use care to dry each part individually using lint free towel or cloth.
VaIves in particular must be cleaned with lint free materials and checked for lint or dust before placing back into instrument
Do not be concerned about residual moisture left in slides; it can be blown out of water key (spit valve) after assembly.
4. Lubricate and reassemble
Put SLIDE GREASE or Vaseline on tuning slides. Completely coat the part that is inserted. Failure to use grease will result in frozen/stuck slides.
Slide grease can also be used on the screw-on caps to keep them from getting stuck.
Put Valve Oil on valves before placing in horn. NEVER use slide grease or Vaseline on valves. Valve oil prevents corrosion of the inside of your instrument. Be sure to keep valves oiled regularly. Once a week remove valves and rinse with water to keep them from sticking. Remember to oil.
Be sure to depress valves when inserting tuning slides or replace slides before putting the valves in.
5. Wash Mouthpiece
The mouthpiece should be washed more often than the instrument. Mouthpiece brushes are available but not necessary if mouthpiece is cleaned regularly.
The mouthpiece is the only part of the instrument that can and should be boiled. Boil for a few minutes at least twice a year to keep sterile and germ free. Also boil mouthpiece after a cold/flu.