A corset doesn't help unless you are relatively low-fat already...it won't hide a gut, for those of us with tubbie tummies...
That said, I do use foam pads, and they do make a visible difference. "Bubbles" I think is the brand, the basic set comes with a stretchy shorts w/ two oblong pockets, and a matching pair of oblong pads which are about 1/4" (6mm) I think...not enough to even notice, but their extra pads are round, and 1/4"--3/4" thick (depending on what size you want).
I put the 3/4" against my hip, and a 1/2" on the butt, and use the oblong one to "blend" the extra bumps between the different sizes of pads. They don't move during the day, and I hand wash the shorts every other day for cleanliness.
The thing is, once you start wearing them, you have to be consistent or people will notice "Oh, not wearing your hips today?"

Without hips, I can wear a size 12 pants...with hips I wear a size 16.
Supposedly there are silicon hips out there custom-made to your dimensions, but at $300/set I defer to foam...

Dress-tech is another brand of silicone pads I might upgrade to.