If you were going for that hand painted look, rather than computer generated, my guess is after you research the right fonts for that era (finding examples on other items) then sketch it out on paper for spacing, etc. That's the time to notice 'oh that S really curves that way' and stuff. Looking at the shapes of the negative spaces (ie the spaces between the letters) can help for accuracy and spacing of the letters. Cut out your own template to wrap around.
Now I never have used the type of paint (unless it also is oil paint) but I would put a really light coat on with the template to keep from getting ooze under it, and then remove the template and put a second coat on by hand after the first is dry. Work from left to right (if you are right handed) steadying your palm against the piece--you can also fashion a mahlstick to steady your hand at a different angle. Take your time, perhaps doing a letter a day. You need a lot of concentration and after a letter or two if you are tired, that's when your hand will shake. I would practice using synthetic small filbert or bright (the shape of the brushes) synthetic sable brushes to fill in or straighten the edges. When I say small, I use #2 or #4 brushes for better control (at least for me the small size works).
That's how I would do it, but I am not a sign painter, but have used lettering on some of my paintings. Perhaps the sign painters on the list will have better suggestions...
I think it looks just fine btw.