When using the dimmer with an add-on switch (not a dumb switch) and no Neutral, you should hook up the wires like this:
Dimmer switch:
| Port on Switch | Wire to connect |
|---|---|
| Line | Wire that is always live |
| Load | Wire that goes directly to bulb |
| Neutral | Empty |
| Traveler | Wire that goes to Traveler port on Aux switch |
Aux switch:
| Port on Switch | Wire to connect |
|---|---|
| Line | Wire that is always live |
| Traveler | Wire that goes to Traveler port on Dimmer switch |
Its essentially the same thing @JohnRob posted. I modified your original picture to help clarify. Pretend the yellow wire is actually white:
