Most standard glow plugs will only draw 3 amps max. There are a couple Supercharger plugs like the P8 that can draw about 3.5 amps, but a normal #3, #5, #8 and F will not draw any more than 3 amps. Now, it can take a lot less to fire, but that depends on things like the tamperature of the engine, outside temp, fuel mixture, and if the plug is wet or dry. If you're setting up a glow heater to fire a 4 engine plane, you should plan on at least a 10 amp system. To get that kind of juice from 2 volts, you're probably going to need a regulated DC power supply.
If the glow plugs are exposed, you might be better doing each engine separately. I've never tried glow engines in a 4 engine plane. It was rough enough starting / sinchronizing 2 in a P38 and Mosquito.