I've been thinking about this, and will amend my original comment to reflect the following:
I was mistaken in thinking that the affective action was hip flexion. I realize that it is mostly pelvic extension. When your bent over and doing those types of movements the femur swings back and forth, almost always in flexion relative to the pelvis. The pelvis, however, tucks into extension, which is the opposite of APT. Moving between extension and flexion helps remind the nervous system "where everything is," and also reminds it that it is capable of doing more than that 1 dominant pattern that it always does. Incorporating side to side movements (or exaggerating the rolling of the pelvis) should further improve the effect. Pertaining to the crab walks you mention as well, in this situation variety is key.
 
As this is a posture forum, however, I will also say that fixing your ATP with this method will only work for as long as you're doing it. If you're not effectively carrying a balanced load in the head, neck, and shoulders, the low back stuff befins re-asserting itself as soon as you stand up. I believe if you want a sustainable, long term, less effort remedy you have to figure out how to carry your load.