I've used a moderate (not really stiff) wire brush to gently remove the majority of the foam stuck to the fiberglass backer, then spray on the adhesive and allow it to tack off. The residue of the old foam hasn't presented a problem on those that I have done. I would suspect any solvent would affect the compressed glass mat and could create a disaster.
After that, positioning is critical because you really only get one shot at dropping the new material into position.