i fully agree with letting them dry out a bit.
i have however quoted on another thread that my seedlings are taking between 30-50ml twice daily...they are in small pots under an HPS and dry out fast....the pots wigh pretty much nothing when i water them.

watering really is just somthing that you get a feel for, the more you grow.
everyones heat/drainage/soil(retention)/plants will be different so, to say that a plant/pot thats a certain size needs "x" ammount of water daily isnt really a very good guide.

moisture meters are a really good idea, i use one myself now and then or just to double check, but after a while i can just tell, its like a sixth sence that developes lol