I have the exact same machines as you do and love them both :) You can do free motion embroidery with both these machines. Thread painting looks so beautiful. I have never tried it though, perhaps one day :)
You can do it on any machine that does zigzag, it is very easy, just very time consuming...****
One of my best friends who lives close to me excels at this. Self taught as well. I'll link to her site for you to see some of her work. It's even better in person. If you click on the pictures you can see more detail close up.
I found this. It's funny that old fashioned machine embroidery is now called thread painting.
Here is an excerpt:
Thread Painting
Thread Painting is an embroidery technique that can be used by both hand and machine embroiderers. In both methods, the technique relies on long, smooth stitches and intricate shading to produce the stunning results.
Machine Embroidery
This is also called free-motion machine embroidery and is stitched with the thread dogs dropped. This offers you complete control of the fabric, and it does not make any difference on how you set the machine for stitch length and width.
It can be stitched using a specialist embroidery machine, or on a normal sewing machine.
You will need to insert the free motion foot and loosen the upper tension to about 2.5. Fill the bobbin with fine thread and use a slightly heavier (about 40 weight) thread.
With thread painting, you draw your design onto the fabric directly and stitch it. You may want to have a separate copy of the pattern next to you that you have coloured in, so that you can follow the shadings you want to use.