I have never used straight-up betanol, but when I utilize Instant Honesty (which I have read contains roughly a 70:30 ratio of betanol to alphanol, among other things) I like to go for 3 sprays. Your mileage may vary though so you may want to consult this post about finding your sweet spot: How to find your sweet spot...
As for the ratio, that would depend what effects you are looking for. I find that higher alpha is better for getting people chatty, but I tend to extract more interesting information using higher beta. Note that in most cases you still have to initiate conversations, but you may find that it’s easier with the help of these social mones.