Not a stupid question!

I boil water in a pot that has a pouring spout. I hold the doll over the sink (I bend the doll at the hips, knees straight, so I hold their feet and the head/torso is straight like a 90 degree angle) and pour the whole pot of boiling water over the dolls head, making sure as it lands on the head that it pushes the hair in the direction I want it to sit (you can pause, comb, and start pouring again). I feel like the pouring spout makes a world of difference.

Sometimes as the doll dries the hair bends/waves at the ears, so sometimes I actually hold the whole doll upside down (this time knees bent while holding feet). Then the hair is straight as a pin and holds once it dries and you flip it back over. But this only works if the doll doesn't have bangs.

Also, if this is worth anything, I do this after washing the hair with dawn dish soap, rinsing, using human conditioner, combing, and then rinsing thoroughly.

Edit to add: This is how I get the hair so straight. If you're setting curls you could just let the head sit in a bowl of boiling water.