Basically what I do. On T190 and smaller, there are two plugs, one on top and one on the bottom. Remove both and drain. I normally just do something else for a 1/2 hour or so and let it drain. I fill from the bottom forcing the fluid in with a syringe with the top plug out. Once full I put the top plug in, remove the syringe and install the bottom plug. If your quick, you don't loose any fluid. Bobcat use to supply the syringe with a kit to change the fluid. On T250 and larger, the plug is on the outside. Rotate the plug to the bottom and drain. Once empty move the plug to 1/2 to 3/4 up and fill until full. The syringe works nice here too.
