For starters, there is no right or wrong way of doing something when it comes to doing a make-up application, as long as it's done in a hygienic way.
What you're describing is perfect for doing your own make-up.
However, the "warming" or "activating" a foundation is a myth due to how foundation ingredients are currently formulated, regardless if it's a liquid, creme, or powder. I've done a lot of editorial fashion make-ups in the late 90's to mid 00's and I've worked with a lot of flamboyant MuA's who did the "warming" and "activating" thing and that was their schtick, technique, thing, whatever they called it that sold themselves apart from other MuA's, y'know showmanship, as you know it's all egos in this small make-up community.
Friction is what warms up a foundation when it's almost frozen, and that's what a palette and spatula are for. Shaking a foundation is what activates it in terms of mixing it up in the bottle, tube etc. in truth, there is no "activating" a foundation, even when you put it through an airbrush. Damp sponges work well in thinning or building up a foundation, so there are options.
No Professional Make-up Artist puts foundation on-the-back-of-their-hand or use fingers anymore as it's very unhygienic, messy and looks very unprofessional, and this was way back in the early 2000's. Now after the pandemic, it's even more so, it's even written into contracts with all the actor and crew unions now. And we all know how demanding actors and brides can be now, don't we, lol.
Anyways, the thread here is a poll on what tools do we use to apply foundations, and fingers are tools as well.