Spinning studs on barracuda grill, any tricks?

Grind off the nuts.
Usually the studs are a very coarse thread so they should back out of the grille.
Back them all out.
Then work at getting nuts off.

Grab stud with a vise grip and turn nut til it reaches vise grip, should be enough space to grab it below nut.

All this takes time and patience, different situations need different methods.