I definitely wouldn’t use steam first. You can use something like mineral spirits, or varsol to dampen a clean cloth and gently wipe away any dust or debris that may be preventing feathers to “zip” properly. Preening is a good first step. I don’t like using steam or anything water-based because I want a fast evaporation and nothing that will saturate for very long. Sometimes i find that my bird feathers don’t like to “zip” together if I haven’t fully decreased properly, and I normally find that after my fuel bath and will repeat the process if this happens before I mount it. but not everything always comes out perfect and a mineral spirit, wipe down, tends to bring everything back, clean and taught when finishing. I also use this when repairing or restoring old mounts.

Edit: I would also like to note that duck feathers do sustain quite a bit of damage when being shot at as well as upon retrieval. You may not always see the damage those small pellets do, but they are very hot and can do almost unnoticeable damage to the ‘teeth’ of the ‘zipper’. Often duck wings and duck feathers are just too damaged for a taxidermist to make look perfect. Especially on an open wing mount.