IMHO you can get by fine without messy pumps, tubes, etc.
Plastic gear oil bottles will 'squirt' even straight up when you squeeze them, and they have those nice pointy nozzles on them.
Squeeze what you can out of the 1st container, then top off 1st container with oil from the 2nd container, and so on...

Tips:
1) Place jackstands under frame, and let axle drop for best diff access.
2) In the winter, warm up the new gear oil in advance by storing it inside. It will squeeze out much easier and faster warm. You can use the microwave oven if you forget.
3) Teflon tape on the plug threads will make them easy to remove the next time.

Now, if you want a challenge, try refilling a 124 manual tranny...
Best of luck.

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1986 300E 5-Speed 240k mi.