Everyone has their own methods for making the dice work better for them. I should say willing the dice to work better for them, as you can not make the dice do anything. They are willful little creatures, will take offense at your attempts to "make" them do anything, and will show their disapproval by rolling you all 1s all game.
What works for me is to always call missile launchers rocket launchers. The reason being that missile launchers have the word miss in them and are therefore more likely to miss. That and sacrificing small warm-blooded creatures to the dice gods. Yep, that has helped me a ton, and is the main reason I do so well in Warhammer games, despite my own ineptitude at strategy and formation/planning skills.
I would try out different rituals/techniques, and it seems you have already found one that has helped in using a dice cup. Also blood sacrifice is always a good one to try, If I may be so bold as to suggest.
P.S. - I have also found that melta weapons hate me. I have never rolled anything other than a 1 with a melta weapon, barring a few extreme abnormalities. I theorize that the same may be true for certain squads, their opinion of you affecting how they do in battle. Maybe try treating your squads differently, or else equipping them differently. Plasma weapons love me and Heavy Bolters are my mistress.
P.P.S. - Also, I find that good rolls are an extremely finite resource and that you must use all your dice equally, lest the used ones become depleted and bad, and the unused ones become jaded and jealous, so that when you do use them they will be bad.