Mls, I haven't had any problems with it. Rust corrosion itself breaks down metal. It's best to get rid of it for the most part over night than to leave the rust and tarnish.
OP, NeverDull does work really well, too, depending on what kind of plating the hardware has =)
Sweet! Thank you all for your help. I didn't get it done yesterday as it seems like this is going to take some elbow grease and time which is difficult with the sick small child. But now I have a good project for a rainy day. Then its onto the saddle
One of my hobbies is working with leather, I love making things or restoring old leather. One thing I was told about it when it comes to water was...the animal had been wet or rained on at some point....its a skin and will dry, it wont fall apart.
I have found it safe to a point for leather to be wet before it starts taking on a 'aged' look, but is more common in softer leathers rather then harness leather. You should be safe to soak the bridles to make them pliable, but once they dry, they will more then likely go stiff again....they need to be cleaned and thoroughly oiled to make them supple again, which probably means doing A LOT over a few days if its really stiff.
I just did this with some old leather halters and they are as good as new.
Oh...one more thing...if its is very stiff...dont force it, it can snap, crack or break very easily!!
Ok well THIS is my specialty! Kay first you said theres mud. Hose it off. Then use glycerine soap on it. Until you get all the dirt out. Then apply a coating of some kind leather care cleaner or lexol glycerine or leather new will work. Then get some leather care conditioner (you will LOVE this item!) and smother the whole thing with the oil. You may have to apply repeated treatments. As I had to do with a old crosbey saddle. For the bit soak in HOT water take it out and scrub it either with a cleaning tool or I use my finger nails and scrape off the gunk. Then dip it again in HOT water take it out and rub a towel really hard through the pieces it will shine right up.