How to mask natural metal finish?

My experience is that it will lift. If you are determined to use this paint, I recommend putting down a good coat of primer, something like Stynlyrez, and let it cure well. Even then you may still see some paint lifting. Those Testors metalizer paints are notorious for lifting, but I have not tried them with Stynylrez, or even anytime recently. I typically use Alclad for NMF finishes And have not had paint lifting issues with that brand.

Try Postits.

There's a couple options here for varying panels.

The first method I found (accidently!)...you can mask off particular panels, then spray just those panels with a primer. Unmask and spray your Metalizer. Those panels that were primed will look a bit darker. This method is a throw back to when I used rattlecan Metalizer. You can see the difference on the outer wing panels, the darker panels were primed first...just grey primer. (the pic does exaggerate the difference a bit)

This one was done completely freehand. Started with an overall coat of "Magnesium" then went over different panels with different shades, spraying a random/mottled pattern, leaving some of the darker Magnesium showing.

This, most recent one, was a combination of masking of panels and freehand, as described above.

When I do mask, I use Tamiya tape...I stick it to the palm of my hand first, to detack it a bit. Most often, I don't have a problem with peeling up the paint. I have found that if I seal the metalizer with a lacquer gloss (I use Minwax, thinned 50/50 for airbrushing), I have zero lifting. You could also use the "Metalizer sealer"...it is just gloss lacquer, so it's far cheaper to get a quart of Minwax. I use the Minwax for all gloss coats. The quart cost about the same as 2 bottles of the "special" metalizer sealer...I've done somewhere around 150 models out of that quart and am just finally getting close to being only half way through it!

While I also find post-its useful, I try very hard to complete the painting of non-nmf areas first, then mask them off before applying the metalizer.

I use blue tape to mask my rattle can Testors Metalizer airplanes with no problems. I never get any lifting of the paint. The entire airplane in the following photo was painted in Metalizer Aluminum Plate prior to masking. There was no lifting of the paint after the tape was removed. Now you may ask why I did not  reverse the taping??? That is a good question. All I can say is that I made a really dumb decision. I will not repeat this mistake.

Go here to see, in great detail, how I did it: http://cs.finescale.com/fsm/modeling_subjects/f/2/t/170323.aspx

In a nutshell, this how I did it:

1. Prime the model with gloss black paint. Sand the paint super smooth before applying the Metalizer.

2. I use two colors of rattle can Metalizer, Aluminum Plate and Stainless Steel. I apply three coats.

3. THIS IS THE TRICK TO PREVENT LIFTING. When the paint is dry, I buff the paint very hard with a paper blending stick. This makes the Metalizer very shiny and very durable.

3. I use blue tape. First I stick it to my work surface and lift it twice before I use it to mask the airplane (see the photo above). This removes some of the adhesive.

4. I lightly brush the final product with steel wool to imitate the natural grain in aluminum plates.

T