I've never used a fire extinguisher before and I was afraid it would be too heavy and unwieldy for me to handle. But it was easy. Pull pin. Aim. Pull trigger. I was able to stabilize it on the ground so I didn't get bowled over with recoil. The poof of stuff that came out was pretty exciting. And after the fog cleared it was easy to see that the transformer had stopped smoking and crackling. Yay! I'm a hero.
I have no idea if what I did, i.e., taking the time to move the transformer then taking the time to turn on fans, was the right thing to do, what the professionals would recommend. I took the chance and it worked for me in this instance, thank goodness.
The living room smelled noxious for awhile so I took that opportunity to lock myself in the master suite and take a shower. Luckily it's not raining, so I could open every window in the house to air out the smells. By the time I finished cleaning myself up, everything was fresh.
The lesson for today kids is to make sure you know where your fire extinguishers are and that you know how to use them. And if you are petite, have a smaller one on-hand alongside a full-size one. (I did use one of our smaller ones, but it can still be intimidating.)