The solution depends.
If you were in a large garment post liposuction now it might be time for a medium.
With liposuction this might also look like adding foams.
If you are a few weeks post op this could look like tailoring the garment to fit your new body (taking an inch or two off)
If you have more than one of the same stage garment it could be time to move onto the next (ie: from stage 2 to stage 3 )
If you had a tummy tuck your answer for compression is patience. You can only compress so much without it rubbing onto your fresh scar. The priority for you is to heal (and not open). Until your incision looks like skin (versus thread at the bottom of your belly) a faja is likely not in your vocabulary.
Keeping a low sodium diet looks like READING THE LABELS, you can not assume something doesnt have a boat load of sodium.