My EK res have more than one hole in the top, so i have a little made small filling tube with aprox 25cm of hose, a 90* angle and a fitting. Then i just plug that in one of the holes i don't use in the top of my res, and secure the end of the hose to the top of the case, and fill it that way. The tube is long enough, so the water doesn't spill out that way, when i turn on the pump
So fill it up that way, bleed the system, and top the res up after that.
Edit: Seen in action here:
https://www.dropbox.com/s/vqp7osj1u21q84q/Res fill.jpg