I also use the pot of boiling water to heat the tubing. I used the hair dryer for a while, but most of my family, (animals included,) didn't care for the noise. One other thing I do is cut the hoop into two equal pieces, then connect them using two couplings. That way, you can twist the hoop, making it collapsible.
The hoop in the pictures is only 1/2" tubing. I made a batch of smaller sized hoops for my daughter's upcoming Hawaiian themed birthday party. I usually use a 3" piece of Velcro wrapped around the hoop to hold it closed when it's collapsed.