I learned quite a bit about reaction from the acting classes I'm taking.
There's a famous quote that's attributed to both Sir Laurence Olivier and George Burns, depending on where you look:
The secret of acting is sincerity.
*Pause for dramatic effect*
Once you can fake that, you've got it made.
So I'd say that with writing I sometimes build on pretty solid personal reactions but sometimes it's a pretty thin sliver and I'm faking the rest.
For this week I ended up writing in the persona of a female singer in a band. So that was definitely different. I don't have any direct personal experience to call on, or even any secret fantasies to fall back on. Although when I come to think of it, there might be some very interesting learning experiences to be gained if I could be KD Lang for a day or two.... What a voice. But I can of course relate to the theme of the singer in my lyrics having to put up with something she didn't like in order to gain something else.
But did it make it easier than a blank page? Yes it did. But was it easier than a regular, less involved, assignment? I don't know. It was definitely fun to do, but it also took some time away from the writing. Swings and roundabouts there. But I've also done a little bit of acting (we took one production into our toughest and most notorious gaol - that was quite an adventure all on its own!) and I've written commissioned works for the stage, and directed one of them too. So maybe I already use your approach more than I realise?