How can a witch/wizard disguise themselves, excluding Polyjuice Potion?

There are several ways that I know of that you can use to disguise yourself without polyjuice potion.

The first -- and the one that fits best for Fantastic Beasts -- is you can use transfiguration on yourself. Aurors are formally trained to do this. Tonks was an expert in this, and got top marks in her auror training. In The Order of the Phoenix, she used this method effortlessly to amuse others. That consensus is held by a lot of others as indicated in this Insider piece, and also in this Quora piece. An extract from the latter:

Tonks mentions in Order of the Phoenix that part of Auror training that she received top marks in was transfiguration disguise [partly due to her genetic disposition :)]. We know human transfiguration is possible at a young age (Cedric Diggory and Krum both used it as part of the Triwizard Tournament). I imagine someone with the power to control the Elder Wand can hold his own for extended transfiguration. He probably allowed himself to be revealed.

A second (and not so useful) way is by using the Confundus Charm on those who can see you, but that requires its repeated use, and the likely scenario that you will eventually miss somebody and be recognized.

A third way (and least useful) is by being an Animagus, and literally changing into an animal. That helps answer the question, but is not useful at all for Grindelwald.