I got the whole set from Amazon back when it was 50% off.
Great value for money. Bottles are 30
ml which is a good quantity for the "price per bottle" of the set.
As for being glossy yeah maybe a bit more than
GW but it's nothing to fret about.
Work well with airbrushes of course but it is preferable to still dilute them a bit. (I use a specific mix for dilution.)
Ghost tints are great. When you want to give special effects.
If you are using them with a paintbrush they are very liquid and go on thin so you will likely need 2 maybe 3 coats to get a good result with a paintbrush.
You can see some work I did with Minitaire in this thread here:
http://www.dakkadakka.com/dakkaforum/posts/list/524844.page