The main reason to bet draws is not to price yourself in. Usually draws have less than 1:1 (or even 2:1) odds
. So generally you're going to be betting very small on the flop, which telegraphs weakness. Instead, check and if your opponent checks behind, you get the next card free instead of for X amount of money. Or, bet a real amount, and hopefully the times they fold and the times they call but you hit will make the play profitable.
As a general rule of thumb, I *never* bet less than half the pot on the flop or turn betting rounds.
So the bottom line is: If you have equity in the pot, worse hands will call your bet, better hands will fold to your bet, or betting will buy you a free card, then you should be betting.