How does one find studs in double drywall
The same way we find studs for single drywall.
Magnetic stud finder

Your drywall has to be screwed in properly.   You will have vertical columns of screws.   When the magnet hits something, go up or down a little, if it hits a vertical column - there is your stud.   Since it is double drywall there would definitely not be skipping of studs so you should be able to mark everything in kitchen in a few minutes.