I know that I may get lambasted for this, but, here's how I do it. I drain 12 gallons into 2-5 gallon pails and a small drain pan without spilling a drop. I first start my tractor and make sure the fluid is warm and has circulated well, then I remove a hose from a cylinder, the longer the hose the better. Now, I put that hose in a 5 gallon bucket and pull the lever back. Fill the pail, release the lever. Fill another pail, now you have 2 gallons left. Shut the tractor off and drain 2 gallons. I've done it this way for almost 30 years and never had a problem.