What methods are used to paint brass photo etch without the paint getting chipped, scraped and/or rubbed off? I've cleaned such parts with 90% iso alcohol, primed with Automotive metal primer and airbrushed acrylics and it seems incredibly delicate. So what are the secrets to getting paint to stay stuck?

There really is no secret. I have found that Mr. Metal Primer from the Mr. Hobby range helps paint stay more durable. Even then, the paint will still be fragile. What acrylics are you using? Some are more durable than others.

you can use photo-etch blacking solution or in the past I have used vinegar to etch the brass prior to priming with Tamiya before painting. Even that is still a little fragile.

I very carefully give a light sand when the parts are still attached then cut, bend, sold or glue, I clean with alcohol and then primer, they are still always fragile but it works well enough....

I use MIG AMMO paints

I guess my experiences aren't unique. Though I'd love to know how armor modelers manage to separate camo colors right over PE engine grills without ripping the first color off. I've thought about blacking the parts first before paint. At least where the pain chips off, it will be dark rather than bright brass. Might experiment with that.

I tried the mention methods and the paint will still come off during installation. Depending on where the PE is going to be installed I will either paint it before or after installation. If it gets painted before installation (like ship railings) I try to handle the PE very little. Once it gets installed I just touch up the PE using a paintbrush.

It is also a matter of what the model builder uses to mask the paint with and how the next colour is applied.
Using a hairy brush means that the masking material must stick to the surface. Using an airbrush the masking can be done with a sheet of paper as long as the paint jet can be directed away from the edge of the paper.
The sticky strips on post-it notes can also be used when airbrushing.
On the other hand: it is possible to get tidy borders between colours with a hairy brush without masking, at least for short boundaries ...
Wet newspaper sticks good enough and is very easy to peel off.
One aspect to consider when masking with non-adhesive materials when airbrushing is "where does the air/paint-mix go afterwards". There needs to be some direction for the air to escape other than going in under, and lifting, the masking material.

/ Robin

Use PE burnishing fluid....if your paint chips a dark PE is better than a brass colored chip.

All of these solutions are good ones. Another option is "annealing" the brass (heating it until it turns red, then letting it cool). That often blackens the brass and makes it less likely to chip off the paint.

Be careful, though, that you don't melt small parts. Annealing will make the brass bend very easily unless you plunge the hot metal into cool water. That returns it to its original hardness (more or less).

I have had good success with the following approach. Most PE parts have some sort of surface coating to prevent them from being dissolved in the photo etch process. To remove this coating, lightly sand the PE while on the fret. Then "pickle" the fret or individual parts in a citric acid bath. The solution I use is 40 grams of citric acid to 120 grams (ML) of water. Citric acid can be found in the canning section of grocery store or at a pharmacy. When the pickle solution is used properly, the part will have a dull color and if viewed under magnification a slightly "pitted" look. I then rinse under tap water and use a baking soda bath to neutralize residual acid. Rinse again under tap water and you are ready to go. Soak times vary by part size, PE vendor, and pickle concentration. When done properly, at this point you can solder your PE parts if you need to do so.
After soldering, I repeat the pickle process to remove flux and residual oils. You're now ready to "glue" your PE part to your model.
Give the finished work a coat of good primer and you are ready for the finish coat of paint. I have had good results doing this with no notice of paint chipping.
Good luck

I prime (Tamiya primer) and paint (Tamiya acrylics airbrushed) on the fret before removing it, then either glue in place or fold then glue in place. I do get some chipping from handling, but once in place on the model, the PE part is mainly already painted, and I just touch it up by brush. PE parts like cranes, and other open structures need to be painted both sides before folding, so I just do everything while still on the fret.

I etch the brass using peracetic acid and then basecoat using Rustoleum enamel.

Thanks for all the ideas. Definitely some good techniques here. I also ran across a review of this stuff:

AK-Interactive Brass Photoetch Burnishing Liquid.

The review was on this site a couple years ago so that is also an option.

I've got a week or so before I need to decide.

Thanks