On my 06 'Avalon I used a Craftsman combination wrench with the box end. On the one that is in back of the bracket I could only turn it about 1/8 turn.So a swivel socket wouldn't work on those hard to access bolts?
Once loosened I used the open end alternating sides to get the best angle purchase on the bolt flat.
I cleaned the bolts by chasing with a die as Sweeneyp but only need to chase one hole with a die.
To replace these three bolts, I used a hemostat and the tip of my finger to hold the bolt in place until I engaged a few threads. Then back to the open end finishing up with the box end.