I installed my own dish for my GUFSDTR500HD too. After assembling the dish, I preset the quad LNB skew to position 3, as recommended in many internet posts. I mounted the dish initially pointing well to the East and with all four cables attached and secured to arm. I then moved it about an inch at a time (as already suggested above) towards the West. MrsA was hanging out of the downstairs window shouting nothing, better, worse etc. Once I'd got the best East/West alignment, I made sure the dish/arm was truly horizontal via the in-built spirit level on the arm. Then I tried adjusting the up/down alignment and picked the strongest signal position. I never thought to try moving the LNB skew.
I think that at the time of installation I had something like 85% to 90% strength and 80% to 90% quality as I remember being a bit disappointed it wasn't all 100%. When we continued from the initial screen, the box then automatically went into a software download mode. Now this seemed to make no progress for ages. Overall took about 15 to 20 minutes, so be patient. After that I think it rebooted and we then had a signal strength of 91% and quality of 100% and everything worked fine.
Hope that helps!