I use Vallejo Matt & Gloss in the dropper bottles and they go a long way.
They are both milky in colour and I mix 6 parts flat coat to 4 parts water in the AB cup. It works great and the matt coat is especially good. It's touch dry in 5 minutes so I do several light passes to get a good build up - especially when using the gloss.
I also use Humbrol Rattlecan matt spray for a quick shot on figures but remember that this is solvent based so make sure your paint has had a good 36 hours to fully cure (at least imo). I used to use it on my builds but it was darkening the paint quite badly. I don't use Future/Klear (for the record).
If you don't have an AB then acrylic rattlecan flat coats are available too from Vallejo.
Hope this helps,
Ben