I used liquid. I guess either would work it's the same basic ingredient, if using a gel when rinsing take care to expose to water longer before handling as well on the inner tube. You don't want to leave trace elements behind.
I guess I should elaborate on this part as this is becoming a "how to thread" .
As with any chemical it can be caustic. You must make sure to rid the part you are stripping of any residue, even any remaining anno you could not get off in a crevice can retain some of the chemical compound. In this case Drano. You can let the part sit linger in the Drano to soften up the remaining anno, once again the part will become very dull while soaking. Brush them up once again in the running water after the rinse to brighten.
Besides a running water wash I did leave in a "pail" of water to help further dilute any remainders, then once again a good running water wash. Then parts must be dried prior to installing back the switch and tail cap, clip etc.
EDIT to add. The inner surface of the tube will discolor. I took a rag/wash cloth and while wet ran it through a couple of times, as well as a few passes while drying with separate rag, it seemed to remove most of the dullness, perhaps onward to a bottle scrub brush next time around.