There are mainly two ways to make baremetal.
I assume you know your way around ur painting program.
The first one is handpainting..
Basically you either use a gradient then u pick colours from the photo. Then you have to start dodging and blurijng and smuding until it looks good.
The second way is photoreal..
Here you cut a piece of metal from the fuse and clone it across the fuselage..using the eraser and clone tools to make it look good. You might have to use smudge and stuff to make everything blend in.
Now onto the alpha.
Most people use a SUPER Strong alpha layer. But i would not recommend it. The alpha layer does not show at night or at dusk.. making ur plane look like painted grey at night

However, I suggest a medium alpha to accompany the bare metal

Bare Metal is never easy. I suggest looking at Daniel Halpern(SGA) or Ben Hewitt's(POSKY) textures. They are good baremetal painters
