I like to use SnJ, Alcad, and Metalizers. Metalizer aluminum, isn't that great, but they offer many other helpful colors such as gun metal, titanium, burnt metal, and burnt iron which produce great looking finishes.
My favorite brushable metallic finish is Humbrol. Humbrol is easy to apply and usually only needs one coat. I also like MM, but some colors like chrome silver and aluminum aren't that easy to apply.