www.lascofittings.com
You may have gotten away with it with no issues so far, but you shouldn't use Teflon tape on PVC threaded fittings or you can cause the female fitting to crack, which would be a very bad day for your pool return. Use something like RectorSeal No. 5 Pipe Thread Sealant.
"The right way to assemble a threaded PVC joint-Schedule 40 or 80 is finger tight plus one to two turns-no more. Two turns past finger tight plus the stress of the system pressure is within the tensile strength of one-inch PVC. ([1,788 psi x 2] + 2,000 psi = 5,576 psi).
Don't use Teflon tape, Teflon paste or pipe dope. Do use a sealant.
Teflon tape, Teflon paste and pipe dope is intended for metal pipe and fittings. Metal to metal fitting joints are more difficult to tighten than plastic; the surfaces tend to gall without the aid of such lubricants as Teflon or pipe dope. Plastic fittings do not need this lubrication.
When Teflon tape is wrapped around plastic male threads it adds to the strain and tensile stress. The tendency of most installers is to incorrectly wrap several thickness of tape around the male threads, increasing stain and stress further.
Teflon paste and pipe dope, just like Teflon tape, make threaded joints slippery. Their use on PVC fittings can be an invitation to over-torque.
When working with threaded plastic fittings do use a proper sealant. The right sealant for threaded joints is non-hardening, compatible with plastic and doesn't add slipperiness.
A non-hardening compound is forced by water pressure into potential points of leakage, thereby performing a true sealing function. Tapes and hardening pastes permit a leak path to develop when a joint is backed off, mechanically flexed, or expands with rising temperatures."
Assembling Threaded Plastic Fittings | LASCO Fittings
I use the bar of a screwdriver because I have 45 of them laying around. (I tape the snot out of the pointy end of course, you KNOW it's gonna drop)
The only downside is it makes blowing out the lines a two person job and one of them is going to get soaked (not fun when water is cold 
).
I wil drain my IG being built below the returns, so the ones Magiteck posted work for me. When we moved and inherited an Above Ground I was so excited to try the often rec'd duck plug but was really disappointed with how chintzy it was. Then it failed over the winter to seal the deal. No biggie, the plumbing was above ground too and I was tearing it down anyway.
I didn’t have any luck with the bungee plugs. The plug won’t screw in deep enough for the o-ring to contact the mating face.
