To print things air tight you need to have extrusion set correctly with the proper amount of infill and perimeter over lap and number of solid layers to ensure no leaks. Also a quality filament that does not change diameter (altering the amount of extrusion). When all is correct you can produce sealed items as printed with no post sealing needed. The idea of going out and buying a printer with zero knowledge of the process so you can print masks is not really very sound. First because a single printer is not going to be able to produce much and second, the process is not plug and play like buying an ink jet printer.. I own a good printer and have been printing for a long time and see no value in my making these items. Shops with 10 or 20 printers, sure, but one is not all that beneficial.. To answer your questions you best bet would be one of the Prusa printers which are the closest you will get to plug an play with good support and software.