An engine will run for several hours on any battery with enough current capacity to crank the starter. There's no need to trickle charge the battery for the few minutes it's going to supply ignition power during a break-in run. Ditto for the generator- - - -using it as an idler for fan belt tension won't hurt it at all. Fill the float chamber through that big vent tube over the choke plate until the gas runs out of the small hole in the casting you mentioned. The engine should run for a minute or so at idle on the gas in the float chamber if everything else is working right.
You need to have the engine tuned as well as possible before the first start- - - -no tinkering with valve adjustment, ignition timing, etc. while you're doing a run-in on the camshaft. As soon as you see oil pressure, bring the RPM up to around 2K and hold it there for 20 minutes or so. Run a big fan in front of the radiator, or trickle water from a garden hose over the radiator to prevent overheating during the run-in. Once the cam break in run is done, then you can deal with fine tuning like idle mixture adjustment, ignition timing, idle speed, and such. Good Luck!
Jerry
