Quail - I have TOO many and can't tell boys from girls!

Can anyone help - either by telling me how to sex my quail, or by taking some off my hands?! I helpfully bought a complete mix of eggs and incubated them (more successfully than expected), and bar the odd mishap with the spaniel, still have around 20 left. They are gorgeous, such cheery,easy little birds, but a bit overcrowded, so either I need to *sob* cull the males or sell some. Obviously don't want to cull any of the girls, but it isn't that obvious which is which. I have coturnix, golden, pied and texan white.
If anyone wants some, I'm near Reading (twyford)

 

At about 3/4 weeks old Italian quail are easy to tell apart. Google them and you will be able to get some photos up which should help.

If they are all the same age and you have more than 1 of each of the breed then you should be able to compare the golden ones with another golden one and like wise with the other breeds. Its no good comparing a golden with a texan. Generally the males are smaller and more slender than the females. The pied an texan maybe more difficult to sex.
When you lift the tail feathers of the males hold onto them for a few moments and they will secrete a white shaving foam substance (although to be honest im not sure if they will do it this time of year)
Again with the crowing, they all stand tall chirping but the males do crow, again mine are not crowing at the moment as there is no action going on  Its difficult to explain the crowing but when you hear it you will know as it much different to the chirping.

Can you upload any photos?

Failing all of that, wait until the spring and all will become clear.

Will the white shaving cream only work if they are sexually mature about 5 to 7 weeks old?