1940s Spark Plug Cleaner [Restoration]

This spark plug cleaner restoration took much longer that I thought it would. This tool is a 1944-45 Auto-lite or Autolite Spark Plug Cleaning Service machine. I bought this locally in Saskatoon, SK, Canada and thought it would be fun to restore. The tool is essentially a localized sandblaster for the tips of spark plugs. I went with several coats of filler primer in hopes of covering all the pitting and denting, but I feel like bondo may have been a better choice. I was not able to get the pressure gauge open to have a look and see if anything was damaged or broken. In the end, the machine worked great, but the gauge did not show that enough pressure for optimal functioning was there. I do not know if this was a gauge issue or a leak somewhere else. I have not been able to find any documentation or manuals for this tool so operating it was just based on how I think it should work. I can see myself actually using this when I come across more gas-powered tools. If