Illustrator users, if you haven’t looked at Veerle’s blog, do it now. Veerle has loads of good instructional content for you to peruse. Her tutorials are quite good, and she includes plenty of excellent illustrations. I looked at one today that might be very handy for you, “Swirly Curls in Adobe Illustrator.”
In step 1, you don’t really need to copy, paste in front, and then rotate the copy. I used the rotate tool with the original spiral selected. I first clicked on the middle end point of the spiral with the rotate tool. Then I released the mouse button and moved my cursor to the outer end point of the spiral. Press the Option/Alt key, then click and drag down to rotate a copy of the spiral. Release the mouse button first and then the Option/Alt key to leave a copy behind.
I messed up step 2 at first because I assumed you needed to hold the Shift key when you scale the 2nd spiral. I was wrong. You actually get a different effect when you do that. If you want the thick and thin to change as you go around the curve of the spiral, try holding the Shift key when you scale. It’s a similar effect to using a flat sided pen nib when you draw. If not, follow Veerle’s instructions. You do have to futz around with the scaling a bit to make it look right.
Veerle adds a nice little hidden shortcut about using the spacebar if you want to move the spiral around as you draw it. You can also increase and decrease the number of wind segments in the spiral as you drag by holding the up and down arrow keys. To change the decay rate as you draw, press Command/Ctrl as you drag. If you want to dive deeper into the way the spiral tool works, check out “Spiral Tool Mysteries—Solved!” by Jeff Witchel.