The short version is to get a keyhole and keep it. You can run the root using the "whipping" method i.e. pull rod slightly out of the puddle and pause to allow the molten metal to solidify, then bring rod back to the puddle and pause, sort of like stacking dimes. This allows you to control the puddle but is slow compared to downhill. It is important to bury the rod inside the pipe at the bottom to get penetration. Whip the rod up/out slightly then back to the bead in a vertical and upward progression. The top half will not require the rod to be buried as much...gravity.
You can root it without whipping, just get the keyhole and maintain it. If the keyhole gets too large you may need to start whipping it or reduce amps. If it gets too small (the keyhole that is) you may need to bring the angle of the rod to 90 degrees with the pipe or increase the amps. It's all about the keyhole.
I prefer 5P+ the restarts are much better.
Hope that wasn't too confusing.