how many tanks can be painted????

I'd say one maybe two. I don't usually thin it that much. More of an 80-20 ratio. I've heard of people spraying straight out of the bottle with no thinner. Paint drys really fast though.

I am not sure which size of Tamiya paint bottle your're talking. Tamiya acrylic paints come in two sizes, 23 ml or 10 ml. Now I assume your are talking about 10 ml bottle.

IMHO, it all depends on:

1) The size of the tank. The larger the tank(say a M-26 Pershing) certainly needs more paint than a small light tank( say a M-3 Stuart).

2) The complexity of the color patten. If you want to do some shading or higlight, you may need extra paint to mix with darker or light colors.

3) The base color of the plastic mold. If you are building a Tamiya M-4 Sherman, you will perhaps need less paint since the mold already molded in olive drab. However if you are building a DML M-4 Sherman, you'll need more paint because the mold is molded in grey; you will need paint to cover the base color.

Therefore, IMHO, for a 10 ml paint, I would say it can paint two 1/35 Tamiya M-4 Shermans if everythings goes well. I usually make a 3:1 ration of paint to thinner in dilution. My estimation maybe a little bit conservation. You may, with a little bit of luck, have leftover for a Tamiya M-3 Stuart or a Jeep.

Ok, that sounds good. we shot for an M3 & 5 Stuart and 2 Shermans, at a 50/50 mix and did not get great coverage.

On the other hand we were shooting with some wind and using the can for power. I will be using an aircompressor from now on.

And they were the itty bitty bottles