Play as released vassal?

[Neutrino Bomb]

Seems like I can't find how to do that for regular vassals/PU. I can only find how to do it by releasing your own cores and playing as that released vassal. How do you release a regular vassal and tag switch into it? (w/o console)

[Sir Squirrel]

Integrate then release to tag switch

[Mr.M]

You do it exactly by the way you explained in OP.

If you want to be bigger just create the vassal for a first time and give him some of your provinces (DLC needed), annex them and then release them again + choose to play as them.

That way i turned into Wales as England and instantly had half of Great Britain.