Thanks, Dave. You're the acknowledged expert on this. 100 hours to get to mirror? That has me reconsidering jeweling/swirling or going to a brushed steel look until I can afford chrome plating because this Prestina has about 6 separate flat surfaces -- especially if you mean 100/panel. If one were to go for a mirror finish, how slow do you recommend buffing? My DeWalt buffer/polisher has a setting from 0 - 600 rpm controlled by a variable speed trigger. I believe you when you say my 6 inch Ryobi bench grinder is too fast. The specs say 3600 rpm. What goes wrong with those? And thanks for suggesting micromesh. No one before had mentioned that.
A stopgap is to see how well I can do with some touch up sanding, steel wool/rubbing compound and buffing so it isn't a perfect mirror but is presentable until a later chrome or polish. Am tempted to try along those lines without getting to "mirror." Having cannonfodder tell us there aren't shortcuts to a mirror polish means that's most probably true, at least short of buying gear that's worth as much as the machine at this point.
Later add: Paul Pratt is posting a great restoration thread where he shows how to polish a steel panel by machine. Who knows if this is the traditional way because he's self-taught, but his method apparently works. It involves using a high-torque 1 HP electric motor, leaning hard into it and backing the panels with wood so they don't get distorted. Here's the link to that discussion:
Gaggia Orione restoration