I did it for decades. After holding a bucket for about the third time, I decided there had to be a better way. And there is, and it's dirt simple-and cheap.
What "I" did, and y'all can do it however you please, was to siphon it into the tractor. Huh???
Place a piece of carpet or cardboard on the fender, put the bucket on the fender (cardboard to keep from scratching it...), then I just used a piece of 1/2 or 5/8 hose, run to the bottom of the bucket and the other end down into the transmission fill hole. Put a little air pressure in the bucket to get the siphon started and once it was working, walk off and go do other stuff....checking wheel bolts, loader bolts, triple check the front axle fluid level, etc. Most of the time it was about 8-9 minutes to siphon the entire contents of a 5 gal bucket into the transmission. Got bored one day and timed it. Super UDT if it makes any difference and it probably does since the viscosity of regular UDT is a little "thicker".
yeah it woulda been nice to have a pump with a flowmeter on it so we knew exactly how much we put into the tractor, but gotta keep in mind that the boss man was heavily focused on sales and not so much parts and service, if we asked him to spend a dime for the service department, it was almost a guaranteed "no".