How do I age cheap shiny jingle bells?

Maybe try antiquing them with black or brown acrylic craft paint. Do a wash with the paint and then wipe most of it off.

https://sawsonskates.com/easiest-way-to-age-metal/

If you soak the bells in vinegar overnight they should look aged. Wash with plain water. If you have a fan, hair dryer or heater to blow them dry, they won’t rust, either. Soak, rinse, dry. No degree in science needed. ☺️

Here's way to do it takes a couple days put in plastic tub cover with bleach 24hrs,then do same with vinegar 24hrs rinse off set outside in sun to dry do this outside makes fumes

Thank you Jewell. As I mentioned in my other replies, I forgot to say in my initial inquiry that each bell is permanently attached to a 5", 6" or 7" white nylon rope cording. I can't think of aa way to soak them without getting the cords involved. What do you think? I enjoy your comment that 'no science degree is needed'...that would leave me out entirely! Next to Math, Science was my worst subject in school. In college, I had to take non-credit remedial Algebra class TWICE before I could take the easiest required Math course for credit and I barely passed freshman biology with a C- .

Suspend them in the vinegar/salt mixture so only a very little or no cording gets wet. It wouldn't affect the cording anyway. Just that it would need to dry out.

Yes with spray paints. If they are strung, pop X shaped holes into posterboard or brown paper and spray paint.

I wired the dollar store bells with spaces to spray them to allow for movement to coat all sides. With 40 degree weather it involved running outside under the deck for spray paint application and bringing the painted project back in the house to dry.

The bells were very lightly sprayed with satin nutmeg, satin brown and a small puff of oil rubbed bronze. Final gold and darker black edge highlights were achieved with a rub on type wax using an index fingertip. Handling the bells to twist and 6” space the interval had evidence of some wax wearing off, I’m not sure how the more modern metallic wax buff products work. it would be best to clear coat seal the wax if it rubs

Alternatively they might be sponged with thinned acrylic paints for another layer of translucent shading.