You can do it by backcombing with a metal comb so you like seperate your hair off into however fat you want your dreads to be with rubber bands then individually backcomb and tangle the different sections until they become dreads. It takes hours and you need a couple people to do it but you can have normal hair one day and dreads the next. They take a while to really form and become strong dreads but they look pretty ballin right off the bat.
But just make sure your hair is really long because its going to get way shorter than you think and IMO short dreads look really shitty. And it will take forever to get length once they are dreaded cause they get fatter before longer.
If you do it that way you also have to spend some time individually twisting each dread throughout the day though for a while.
Also if you smoke know that your dreads will reek of whatever you were smoking because they hold smells way more than normal hair.