I think you'll find that a satin finish is accomplished by "bead blasting". Some have called it "sand blasting" but that is in error... true sandblasting (using sand grit) would eat through brass "in a wink". Softer "soda" beads (someone correct me... Calcium?) are used which will mark but not erode the brass, leaving a very even "satin" or silky finish. There is another type of "media blasting" that uses silica beads but I think that might again be too aggressive for brass.... probably for fine detail work on harder metals such as iron or steel.
If you can find a picture of one of the horns that Leigh has done with scratch surface/silver plate you'll see something that is very similar to the old "retro" finishes that used to be available 50-odd years back. Yamaha has a satin surface, silver plate option available on their new Xeno lineup. (They call it "matte"... look for 8345RGSM).
A guy named Rich Ita specialises in restoring old cornets and the satin silver finish is one that he has done numerous times. I don't have it handy right now (someone will chime in with it) but he has an excellent website with great photos of some of his restorations.
Don't worry about copying those finishes at all...they certainly aren't mine...it was Leigh McKinney's craftmanship that put it together. You want to check out
http://www.eclipsetrumpets.com and see some of his finish options. Perhaps there are some pictures still around the website here of last year's 1st prize-winner's horn (and accessories!)... truly outstanding and distinctive.