Topper,
Just have a few seconds here so won’t go into a lot of depth for answers. First off, I ASSUME that you are going to receive some formal training…RIGHT?
Hot starts – Keep in mind that about ¾ of the air going through your engine is for cooling purposes, only the remaining ¼ is used for combustion. The amount of air being drawn through the engine is dependent on the speed of the engine (revolutions of the gas generator). The slower the engine the less air is being drawn in. The non-variable is of course the amount of fuel being introduced at engine start. So if your engine is not turning fast enough when you introduce the fuel you can have a hot start. Reasons can include low battery/inadequate GPU voltage. (Neither of which should happen because the pilot is supposed to check that before attempting a start). Mechanical problems with the starter/generator etc can also be a cause but it is the pilot that decides whether to introduce the fuel or not.
Xgen starts – dependent on the aircraft type. Some applications call for xgen start as normal procedure but this of course would be fully covered in your formal training.
Water in jet fuel – in addition to previous comments remember that water goes into suspension very readily with jet fuel. Attempting to drain fuel after the aircraft has been towed etc is a waste of time. The time to do this is after the a/c has been motionless for several hours.