I cover everything at the bottom in kitchen roll, then get a big jug, put it under the graphics card, then unscrew one of the caps on the bottom.
Or, get an M20 to 1/4inch thread like:
http://www.specialtech.co.uk/spshop/...pid-17357.html
Assuming you have an M20 fill port in the reservoir - then attach a fitting and tubing to it, and tip up your case to just use that as a spout.