#some mimes with a good sense of time can host/dehost in a moment where everyone viewing them blinks simultaneously

[creaturefeaster]

How do mimes get into their hosts?

As long as they are fully obscured from view of any sentient being, they can then enter their chosen host.

Their stem expells from their vessel, their head & torso are temporarily stored away as their stem invades & conforms to whatever internal shape is needed to control the host. In the case of a living being, they are assuming the shape of the nervous system network.

The simplest way is through an orifice, but if no inlet presents itself such as in certain electronics, or plants, they can still invade through the atomic level. It's just a more complex and therefore lengthier process. Any eyes on them during the process renders them inable to take hold of a host. Similarly, they need to be obscured to exit the host.