Asking because I need to redo the paint job on my OV-25. Going to go hammered silver color cause that is the original paint that Westinghouse used. Is it a good idea to do that?

Personally I hate powder coat😬, especially when it starts lifting after a few years of the elements!
For all my lanterns in use outside, I have always used auto paint
My GEC on the front of the house was originally moulded in a creamy/beige fibreglass, which after years of use outside starts to expose the glass fibre in it!
I re-sprayed the whole thing using a ‘Rover’, (British car company), beige colour that was similar to the original GEC colour! 😀
It’s still looking like new today 😎

Powder-coating is very expensive, and you’d have to find a vendor who would be willing to do something on the novelty side. Not to mention if you get a scratch or some damage to the fixture (which will happen, wear and tear), it is very difficult to correct.

A more logical and cost-effective option is to use the regular off-the-shelf spray paint. @BT25 has good experience doing this with his Silverliner. It’s easier, less expensive, and easy to correct if there’s imperfections or you get any sort of surface damage to the paint.

Yeah but I've tried different hammertone paints already and they don't show the hammertone look nor do I have prior painting experience.

It takes patience, and practice. Prep work also helps significantly.
I was horrible with spray painting (I used to refurbish traffic signals as a side gig), but I learned and got techniques from other collectors. Nowadays I’m more comfortable and do far better work. It’s not a 1 day job, it’s something that could take up to a week.

There’s a vid on YouTube of someone restoring a OV-15, and what that individual did is very similar to how I’d approach your fixture, minus maybe the little details, like filing craters in the mold.

A subjective option could be leaving it as-is. A good cleaning with Simple Green and water goes a long way. Not to mention you’ll never get that factory Westy paint again, even if it was professionally done.