Lol.... bin there done that.... any chance of putting up a pic of what you are trying to do & results so far?
Silver/Alu/metal finishes are perhaps the hardest colour of all to do convincingly.
There are loads of variables to take into account here, starting with....
OLD can from grandpa.... paint can go off, I'd use a new pot/can of paint designed for modelling.
I think Badger do small paint filters for their gravity feed cups, but first your paint needs total stirring, don't thin it yet.... I use a device similar to a coffee frother/paint stirrer/ small Dremel (on LOW speed) to stir the paint thouroughly. Don't forget to hit the off switch before removing stirrer from jar 
Filtering, fibre-free disposable coffee filters twisted into a small cone held over a paint cup/jar, OR some fine stocking mesh (panty-hose, how you get it is up to you 
).
Pour just enough to use in 1 go, then thin as needed before decanting to your airbrush. Metal paints tend to settle out very quickly esp, when thinned for spraying so lots of agitation is needed.
Then there's the finish of the target: needs to be smooth smooth smooth for natural metal finishes, esp on aircraft .... Alclad say spray over a seni-gloss black undercoat.
Then there is environment: dust is your enemy, as is humidity: spraying in the yard or garage might not be the best place, a dry shower room is almost ideal (just don't let your N&D catch you...), then cover your wet model with a large tupperware (or similar) box, slightly propped up to keep dust off but allow air circulation.