As a trans person: Use trans as an adjective, and with about the same heuristics you would for noting some other aspect of a person.

Sure. To make the purpose of the grandparent comment more explicit: I find that adding object-level positive examples to my suggestions makes people more likely to act on them. If all someone knows is that tranny is a slur, and they want to refer to trans people in general, then tranny is still the most available word. They have to choose in the moment between making their point conveniently and impolitely or spending time determining how to make that point politely (maybe 'people who are trans'? Yeesh, that's so long). Giving them a tool- "instead of using tranny, why not use 'transfolk'?" that respects their concerns (it's hopefully intelligible to outsiders, about as short, memorable, and they have another person's judgment that it's not likely to be considered a slur) signals mutual understanding and is more useful to them.