From here, all you really need to do is stay tight during the descent... you need to make sure that you're going down at a pace that allows you to keep hamstrings tight. I'm not losing that tension in my lats... The easiest way I find to do that is to think about spreading the floor apart. Your feet shouldn't actually move, but if you do that it's going to naturally cause you to engage most of the muscles in your lower body... If that cue doesn't work for you, you might try something else. Some people like thinking of digging their heels backwards, and that helps them to engage their muscles. The really only thing that matters is that you are keeping tight.