Here you can see how I'm sketching a chair. First, I draw the structure for the half of the chair. Then I move the grid away from the camera, and draw the other half. Then I change the camera position, it's now 3d indeed. I rotate the grid to a new orientation, then I change the drawing colour and continue drawing with the seat of the chair. The hatch pattern on the seat can be used for indicating solid surface, just like with 2d drawings.

Then I rotate the camera again for new view and rotate the grid 90 degrees. No I can start to draw the back of the chair in a similar manner than the seat.

Now the chair is finished, it took two minutes.