Best way to "reactivate" a language

[Purangi]

Let's say you used to have advanced speaking skills (C1-C2ish) in a given language.

Let's say these skills became mostly dormant after a few years of inactivity, except for some passive exposure.

Let's say you needed to "reactivate" these skills in order to use them intensively.

How would you proceed?

Cheers!

[Jean-Luc]

I am currently using (in that order):

1) Assimil as a great tool to get back in a language with conversation, pronunciation and grammar for a quick and easy reminder.
2) A "professional" flahscard like "learn with oliver" to work and extend my vocabulary
3) Yabla in order to get an immersion in real life and remind me or discover new cultural traits
4) Watching TV shows like "got talent or the voice" and news
5) Skype-like conversations with natives I find on sites like "wespeke"
6) Interactions with natives living in the country like a tandem with my Chinese neighbour (teach French - learn mandarin)
7) A solid grammar for a full review
8) Travel

[Cavesa]

Tv series work really well, they reactivate the skills in a complex manner, they work on everything, except perhaps writing. Binge watching is the best.
An advanced grammar workbook or equivalent helps me with further reactivation of creating my own sentences and to not speak like a "fluent" neanderthal.
At that point, resources for beginners (=vast majority of stuff for learners on the internet or on paper) are just procrastination and not real help, a previous C1 or C2 speaker doesn't usually forget the complete basics in a few years (if they forget them in a loooong period of time, it's no longer reactivation, it's learning again).