Dumbbell bench press: how to get into position

Question

when I practice dummbbell bench press, I'm afraid more of how to get into the right position than how to perform the exercise.

Precisely, these are the steps that should be performed (images taken from this video):

1. Step 1: The man keeps the dumbbell above its quads.

2. Step 2: The man receives a backward push, generated by the legs (I suppose).

3. Step 3: The man puts his whole back on the bench (in this case inclined bench)

4. Step 4: The men lowers his legs and is ready to start the exercise.

My questions:

1. About Step 2: which are the muscles that have to perform this push?

2. About step 2-3-4: which is the correct position of the back during these movements? Has the upper back to be arched with retracted scapulas? And what about the lower back? Should it be flat, retracted, inarched etc?

3. About step 3 Should the lower back be flat and adherent to the bench, like in leg raises (see the following picture) or should it have its natural lordosis?

When I perform this movement, I feel always low back pain. For me, it's more difficult to get into the right position, than doing the exercise.

Answer 1

So to do the initial push, I would usually jerk my knees back as I go back onto the bench, one by one, but really fast so it seems simultaneous. Also, while you're going back on the bench you want to go back with your scapulas already retracted, so that once your back hits the bench you don't have to adjust. Now for the lower back pain, not too sure about that, never really experienced it when I used to workout and do incline db press. Maybe invest into a belt, if you're seriously concerned about it, do a lot of foam rolling as well just to be safe.