you can slow down the rate of fluid flowing out of the "tank" by making it difficult for the fluid to get out of the hole.
How do you do that you say? Well one way is to find on your tractor the transmission/tank vent. I know where they are on Kubota's (under the seat) and Kioti (built into the fill cap) But I don't know where it is on a New Holland. BUT if you can find the vent hole, Stop it up. On the Kubota and Kioti machines I have done, I used a #8 machine screw. Now without a ready source of makeup air at the top of the fluid column the fluid does not want to come out of the filter hole. You can change out the filter, and take your time. A small amount of fluid will come out, but at a pretty slow rate. Of course the fluid in the filter itself can spill if you upset the filter. Do not forget to take out the stopper screw before you start and use the hydraulics.
Here is an experiment you can do while sitting at a restaurant. Take a drinking straw and push it all the way down in your drink. Now put a finger or thumb over the top of the straw, and pull it out of the drink.. It is a Miracle, the fluid does not run out the bottom of the straw, defying gravity. Now release your finger from the top end of the straw.. here comes the fluid out the bottom.
Lots of other ideas out there, but this one as near as I can tell is all my own and it works.