Firstly, welcome to the forums, cesege! Hmmm… I don’t think i’ve ever heard of silver metal dust before, but i’m pretty sure some one here can help you. I use plain old rattle can colors after the model has been primed. They say you should under coat with flat black first then spray on silver/aluminium… You can also try Bare Metal Foil.
Hey, why not join the Natural Metal Finish Group build in the Aircraft forum, there are a frew guys who are sharing techniques over there! [:)]
Again, welcome to the forum. I’m not sure about poulder, but I’m assuming its like SNJ, that is you apply it to the area you want it with a soft brush or q-tip and then polish it to the sheen you want with a cotton ball. If this is the case, you should have no problems applying a gloss coat over it.
My suggestion would be to take an old model (or buy a cheap model and assemble it) and try what you want to do on it. That way you can find what works with out damaging your Gloster. Word of caution on aluminum paints (whether applied from a rattle can or air brush), you will find that almost all aluminum paints (except for Alcad II) will lift if masked over with regular masking or modeling tapes. To overcome this (especially on those panels that you are applying the poulder to) you can mask with Post-it Notes or damp newspaper, both of which work very well and won’t lift the aluminum paint under them.
I would go with Alclad. I have done 5 1/48 aircraft with various shades of Alclad and am very happy with the ease of application and the final results.