You can also use a syringe and a bit of tubing if you want. I keep one around as a backup in case my pump dies at a contest.

In theory, you could set up a gravity feed or siphon to take fuel from the bottle in to the tank. Some of the guys at my field who fly gas use a siphon-based system to fill and empty their tank.

Some gas guys also use a pressure system, where an air pump pressurizes the fuel bottle, pushing fuel in to the airplane, or creates a small vacume to suck it out.

Just make sure that if you go with any of those options, that any rubber bits will hold up to nitro. Lots of bits that stand up to gas disolve in nitro, and some stuff that handles nitro disolves in gas. Some stuff is good with both.

An inexensive hand crank pump really is the easiest and most reliable solution, which is why the vast majority of people start out with one.