Kovu, another way to "scale in" is that if you are uncomfortable putting your entire amount you want to put in on a single trade/signal, you divide it into thirds/fourths/fifths etc, and then if the market moves against the initial trade, but you still have confidence in the signal, you "average down" (on a Long) on your subsequent trades and therefore improve your cost per share.
Kind regards, -CAPT J
"What would you attempt to do if you knew you could not fail?"