Slip-joints & teflon tape / pipe dope

Do slip-joints require teflon tape and/or pipe dope? According to Geberit's tech support... for their tubular pvc slip-joint W&O fittings, for instance, they say they do NOT recommend use of teflon or dope. However, in an article by Peter Hemp on installing kitchen sink he says to use it (at least for brass slip-joints). So let me ask the experts here... should we use teflon and/or pipe dope on the following slip-joint connections for drains:

1) tubular pvc
2) tubular abs
3) tubular brass
4) pvc pipe
5) abs pipe

I'm surprised Geberit said "no" as I remember being advised in this forum to use, for example, on ABS cleanout threads... which by the way please weigh-in on if you disagree with that advice as well.

Thanks.

Peter Hemp never has been a plumber. He's a homeowner that writes about his own home, believing that whatever comes out of the little head of his is amazing.
Not so amazing when he needs goo to seal his leaks.

A slip joint fitting is always installed with clean parts.

No tape and no goo.

If you have a threaded cleanout plug, which is a tapered thread and therefore can use a thread sealant, then tape or thread sealant that "printed on the can instructions" can use it. Some pipe thread sealants specifically say on the instructions that the oil will do damage to the plastic.
I make sure, that the thread sealant I buy will work with plastic, but then I carefully check to make sure first. If you use the wrong pipe dope on a plastic cleanout fitting, it will glue it in place.

If you are installing a p-trap, it's important that the "swivel" nut is tightened first, and then the other two.

It really can't be said too many times: thread sealants (pipe dope and thread tape) are for use on tapered pipe thread joints ONLY. With the
emphasis on ONLY. If you have some other kind of plumbing joint which doesn't seal without the use of goop, then either the materials or the
workmanship is DEFECTIVE. If you are in some kind of emergency situation, and have only defective parts to work with, there are many other
kinds of goop which will work far better than the usual thread sealant materials, for instance a good grade of polyurethane caulk/sealant.

TEflon tape on a slip joint does absolutely NOTHING, but joint compounds can "melt" the plastic or rot the gaskets. Do NOT use anything other than the slip joint gasket. IF it does NOT seal, it is because you have done something wrong, so fix THAT, do not try to "cover it up" with putty, paste, silicone, or tape.