As far as satin finish, what we do here is bead-blast in a large cabinet filled with bead-blast material using an air compressor to regulate the amount of pressure the gun pushes the blasting material through. The higher the pressure, the more the finish is "roughed up" by the material. The total cost to do this depends on the amount of prep needed ( dent/ding removal, masking off surfaces not being satinized, etc. ) but we charge $125 plus shipping costs to apply the satin finish. After the horn is blasted, it must be completely ultrasonically cleaned, brushed inside and high pressure air blown to remove any remaining material which would hinder the proper operation of the slides and valves. The parts which are not to be satinized such as slide crooks, valve tops and bottoms, etc. are then highly polished. Some examples of this work can be seen here:
http://www.quality-brass.com/webstor...satinintro.htm
There should be someone local to you who can also do this work. Good luck with the project. When plating an entire trumpet in a tank, remember that any plating that gets inside the valve casings and slide tubes will have to be removed or you will be lapping your valves and slides back into the casings and slide receivers to get them to work again.