If you are interested in overhauling your brass instrument please consider that re-lacquering requires buffing & hence removal of material from the overall mass of the instrument. Engraving will loose its edge or in some cases disappear. You instrument will not be the same as it was due to the nature of this removal. You will also have lost any value if it happens to be collectable. So for all these reasons we do not recommend re-lacquering.
Re-plating of silver on the other hand is possible & adds mass & is not frowned upon as re-lacqquering is. But the business end of a brass overhaul are the valves. Pistons can in certain cases be re-plated with nickel to add mass to the diameter. The piston then needs to be lapped & fitted to the valve casing for a snug like new fit which eliminates leaks & helps prevent the instrument from playing flat as long as all other leaks have been addressed.
In the case of trombone handslides, these can be rebuilt using either inside stockings or both inside & outside tubing.