Rule of 2 and 4 is good for the flop and turn you can't really extend it to preflop.

You need to refine the rule of 4 a bit when you have lots of outs. For more than 8 outs, mutliply by 4 and then subtract the number of outs beyond 8. So if you have 12 outs otf, that's 4 outs beyond 8 and you have about
12*4 - 4 = 48 - 4 = 44% equity.