I change zincs, clear fouled lines, etc. with a length of 1/2" vinyl tubing
hooked to the foot pump from my inflatable
dingy. You just stick the other end in your mouth and dive until your friends leg gets tired. You can't do a whole bottom at once unless you have multiple friends. You can do about
ten minutes at about five feet if your friend has good knees. The bellows pump capacity is too low to over pressurize your lungs. (I don't clench my lips.) There is a fair amount of resistance in 15 feet of hose and I don't have any 300 pound friends. I have been doing this for years.
You can also us an inexpensve compressor as long as it is oilless. A diaphram compressor is prefered over a teflon ring piston one since there is no chance of getting teflon dust in your lungs. I do run a teflon ring 110 volt one off the inverter
on my boat for shallow water exploring. I have 100 feet of hose on it and it will support only one diver. Starting it off the inverter
requires at least twice its rated running amps. I use an Airline brand regulator since it is designed to work at lower pressures than the ones used with scuba
tanks. The compressor was under $200 and the regulator was under $100 a few years ago. I am using regular paint
gun hose but I am not sure that this is OK. The hose that comes with Hoka and similar equipment is labeled for "breathing air" you can get it from body shop or industrial supply houses. I also use the inline filters that are sold for paint
gun use. Again, to be sure that you are safe, you should be using a filter that carries the NOISA or Bureau of Mines label for breathing air.
Please remember that you are getting advice from a guy who uses dental floss attached with super glue to repair cuts and tears in his skin, so the above is a describtion of what "I" do and not what is necessarily safe and prudent.