I would probably do 1 or 2 coats of spray poly over the paint. And before I painted all of them , I would paint the most used doorknob in the house and see how it holds up over the course of a few months. I might also do a light coat of primer first.

Prep is key in your paint holding up over time. Some brass hardware is not even brass. Just a coating baked on and a shiny protective spray to keep it pretty. : )
Even good solid brass hardware has a coating.
Proper prep means a good cleaning with soap and water and a fine steel wool to give a microscopic tooth for your finish to adhere and bond. I usually wipe that clean with mineral spirits just to be sure. A good primer, an etching primer is best on metals. Should come in a dark color as you want a bronze dark finish?
Also paying attention to temperature and allowing the proper time for the primer to cure.
Usually the can has a window of time where it is cured and the final finish coat should be applied.
Non of this should be done without proper ventilation and a respirator. NO family members anywhere near this process especially children. Best to set up outside on a tarped table in a garage on a calm day, no wind. Low wind, set up with the wind behind you.
My entry hardware is brass, but good solid quality. I took the hardware off, switchplates, etc
and took off the coating, cleaned well, and gave an overall burnish with fine steel wool and a red scotchbrite in small circular motions over and over a few times. They now have a nice matt finish and a soft patina and a light tarnish. Not fake shiny anymore. Did the same with the stainless plates in the kitchen so they would match the brushed stainless appliances.

That is alot of hardware. Might just want to start with the most offensive areas that really bug you. The entry foyer, kitchen, main living area first. Or in small batches if you don't want to remove the hardware. (i would remove it) spraypaint mist tends to travel airborn and ends up on floors and furniture without notice until too late.

Here is a link that might be useful: painting brass

We painted our brass knobs (cabinet knobs) in the bathroom...to silver. After a year, it is wearing off. I did not do poly over it, but that is a good idea.

My daughter had real solid brass hardware on all her entry doors and removed what lacquer was left with acetone. She had to use very good gloves and soak the handles. (check on internet for more info). They have a nice antique brass look now and she may do an oil rubbed (chemical procedure on internet) finish. She is waiting on trim work and misc before re installing, so I can't speak to how they'll wear. The cost to replace was prohibitive since she has 2 sets of double doors and 4 sliders! I don't think paint would wear well on handles. The lacquer certainly did not.

I spray painted the brass door knobs in my house in oil rubbed bronze last summer. Most of the knobs were for closets, so they don't get a ton of use. BUT I also did the knobs on the double doors leading to my laundry room, which are used several times a day and they show absolutely no wear. I'm so glad I did it. It makes such a difference and you can't beat the cost of a can of spray paint!

Thanks for the feedback everyone! I'm thinking along the lines of "stephf",,,,I spray painted a few knobs....some in high use areas and some just on closet doors. I'll wait a few weeks and look at the wear and then decide to move on or not.

Hmmmm.... My front door handset is shiny cheap brass that is all pitted. I even disassembled it and the lock face once trying to clean it up to no avail. And I happen to have on hand a spray can of textured ORB that should marry with the pitting nicely. The door is rarely used, so I have added a project to my spring thaw list.

THANKS!!!

I had forgotten.....I spray painted all the knobs on our bedroom furniture a few years ago from a brass look (it's actually junk metal) to a nickel look. I had looked into having them nickel plated but it would have been almost $500. I painted the furniture white and figured I had nothing to lose so I did spray prime them...then the paint...then 2 coats of spray poly. Granted it's not heavy use in the bedroom but they still look fine.

Priming and poly should make them hold up longer....

I've spray painted them before and found they wear very well. I think i used fusion spray paint for plastics - it's sticks to virtually anything but of course you want them clean and it doesn't hurt to lighting sand with a sanding sponge.

I did this in our old house a couple years ago. I painted door knobs that got a lot of use -- our front door and back French doors. After a couple years, the paint had worn off quite a bit, even after priming (although I did not use poly). Before we sold our house, we ended up replacing the entry way door handles. Poly might help.

Have done it... sanded, cleaned thoroughly, primed, let cure, sprayed with ORB, let cure, then poly. It's been three years and just starting to knick off on knob where rings hit.

Someone here wrote that it really makes a difference if you can let the paint cure for a couple days between priming and coats and final poly. I really think it does work better if you can do that.