Easiest:
Fill a big, deep jar with fresh fix (big enough and deep enough you can hang several strips without touching).
Using plastic-coated paper-clips (or bent stainless steel wire, available from many hardware stores, or good-quality plastic-coated gardening wire) hooked through the perforations, hang the strips from a piece of wire or dowel across the top. Agitate (raise and lower the dowel) occasionally.
Fix until clear, then for the same time again (don't worry about over-fixing: 5x clearing will do no harm).
Wash, still hung from the clips, in 3 changes of water for 5 minutes each. Agitate occasionally to assist washing.
Hang up to dry, still on the clips.
This keeps the risk of damage to a minimum. I'd be EXTREMELY hesitant to interleave 35mm in a tray.
Cheers,
R.