Seems to have worked OK. Why didn't Zwickels method work. Was my gas line too long (2 mtrs.)
One keg has to stand up a table or something else, the other one on the floor.
In Case that the Kegs are only half full, the pressure gradient (difference in hight) is a little only. That for you have to fill the beer line completely to get a suction on the upper keg as soon as you have connected the lower keg.
What Im doing in that case: connect the beer line first on the upper keg. The beer tube will be filled half or three forth only, because the tube gets pressure inside.
Take a tool to depress the valve at the other end of the beerline til the air is completely removed from the tube.
The tube must be filled completely with beer. Then connect it to the lower keg.
If the beer still doesnt run, there must be an obstruction somewhere in your system.
But there is another way to force the beer run: connect only the beer outlets with eachother, remove the gas line.
Now open the security valve at the lower keg a little, just to lower the gas pressure til the beer starts to run.
Then connect the gas outlets and the beer will continue to run.
...or just lift the upper keg to a higher place to get more pressure gradient.
Cheers