Indeed,
George, you're getting the hang of it.
It does take some practice and a lot of 'trial and error' to be able to correctly judge the correct size of brush to use, dependent on image resolution and background complexity. Something I'm still learning/experimenting with myself!
Another "tip"... something that I *always* do...
I 'extract' on a duplicate layer and once the extraction is complete (an art in itself), I set up "guidelines" based on the original image.
Based on these guidelines, I then use the 'clone tool' (dependent on the size of the original image) to clone back the "bits" that the extraction tool has erased.
Activate your "original" image, centre your brush according to your guidelines and Alt/Click to activate the beginning of your cloning area. Turn off your "original", turn on your extracted layer and then, using the guidelines that you have set up, start cloning back along the edges those pixels that were lost (toggle your layers on and off to get a visual sense). Play with brush opacities/sizes when it comes to the very fine details (whispies).
Even after this process has been completed, yes, be prepared to get out your eraser and (again play with various opacities) dab around those outer fringes. Use your 'eye' and common sense.
I find it helpful to put down a solid black or white background, to see my progression. And yes, zoom right in there!!!