The few things I have learned about alclad is that you need a good quality masking that willnot lift the paint from the base black. I used Tamiya tape for the first time on the mirage and it worked very well.
I also spray at a low pressure, set the airbrush to as wide a fan as I can and lastly spray at a low angle (about 30-40 degrees or so) to the model where I can, this makes for a larger spray coveridge area.
It tends to lesten the streaky effect
The other thing is to get yourslf some cotton gloves when working with the painted model, although the sales pitch says it is very tough paint it still rubs off in places where you handle it allot.
I used no future or any setting solution for the decals, there was not even a gloss claercoat over the alclad before dacaling. I have used the pollished allu on 2 models now and both times the decals showed no silvering at all.
Hope it helps, but I am sure the experts here will be able to give some great advice you need.
Theuns