A partial tutorial. Borrowed ideas too. :-)

Most of the steps to create 2-torus:

1. (Per Pilou:)Do Circle, mirror circle, do tangent circle.
Intersect script, or place points
Edit trim, and mirror little curve.

2. Do Vertical circle for future torus sweep.
Mirror circle, do line and trim to make half circle, for future blend.

3. Remove old green circle, do arc.

4. Sweep half circle and line, with cap ends.

5. Remove fender shape, keep red area, delete curves.

6. Re-Form left circle.

7. Sweep little circle to form torus.

8. To remove part of torus: Do Boolean Diff of torus, with the red
area as the subtract selection. (Do not use red edges or red curves, or
the Boolean does not work.)

9. Cleanup, remove half circle curve, and small circle. (Edit Pictures for 8 and 9 are backwards...)

10. Select top two half circle EDGES (not curves), and do G1 or G2 Blend.
Mirror the Blend to the bottom.

11. Cleanup, and select 4 edges for planar. Repeat for bottom.