Caporegime
When you deadlift, imagine you're pushing the floor away from you and you're just holding onto the bar and pushing down rather than pulling the bar. a Deadlift is a pushing exercise after all.
Also a good warm up for the hip flexors are OH squats which help to "open up" the hips.
I think that helps for everything. Imagine the bar is the stationary item, and you are pushing into the floor/bench. I do this for squat and bench too
RE: That guy with dreadful form deadlift; judging by the size of his legs compared to his arms - says it all really.