I do not yet have a full set of usable original buttons and knobs, and I prefer not to mix and match original and reproductions so i'm going to use all 3D printed buttons and knobs for now.
My 3D buttons are a bit elaborate, they consist of machined brass parts that are epoxied into the plastics, all employ a set screw to lock in place. I didn't come up with the 3D printing design myself, I traded circuit design time with a friend who printed these buttons and knobs, i should have the files somewhere if we need to dig it up for future use. The tone control knob has a minor mistake, there was a 90 degree rotation for the metal insert, so i needed to tweak the knob to accept the insert clocked by 90. The fine detail of the tone knob steel insert needed to be finished up by hand with jewelers files, it must grab the outer control shaft without squeezing it too much.
Once the buttons are assembled they are sanded and washed before paint. I allow the water to dry over night, the 3D printed plastic seems to be slightly porous and i don't want water messing up the paint. The buttons and knobs will be painted the same color as the Dial backplates (Rust-oleum 7771 SAND). I find that Rust-oleum paint is quite durable for contact surfaces that need to be touched daily as long as the paint is allowed to dry for a full month or more before being put into service. There are some paints intended specifically for plastic surfaces that may do better in this application, however I didn't want to buy a new can of something that didn't match the dial face perfectly.
