I used to own one of these things 5 years ago and did my gear oil and ATF fluids on them. It wasn't the best but it worked because of the cramped area, i could get the bottle in at a good angle. I normally warmed up the fluid a little bit to help it flow better.
Today, I was started to do my rear diff and well that pump turned into junk! Did move anything. Luckily, i just connected both hoses and hooked it up the my trunk and let gravity do its thing. I still need to do my transfer case and front diff, i need something easier and less messy.
Ive seen the ones that look like soap dispensers, are they any good?