Okay, let's try to reply to this again without closing the screen this time!
Use long rectangles with one tapered end. You can sew the tapers together and they'll come up to a point. You can change the angle of the taper, though, to change this.
Also, try making just a cuff of fabric for his shiney, metal head, then sewing a cap to one end of it. The fabric here will hardly lie flat and - when you stuff it - will more than likely puff up a bit and give a soft dome effect.
This is all one big excuse to make the world's worst drawing's of Bender, by the way....
For his shoulders/neck are, you could use the same cuff/ring as for his head (one long rectangle of fabric, sewn at the ends to make a sort of tube), but sew triangles onto the rim of it, then sew each triangle together. It'll gather and make that slope. I know it sounds like a lot of work, but it's super easy, short little lines to sew. Here's another picture: XD
He seems like he'd be super easy and fun to do - all those geometric shapes!
I hope this helps!
For his shoulder/neck area, I'd use the tapered rectangles. You can even use the same cuff/ring sort of shape for his body, but