pito:
Not sure the loading with 2x18pF (those basically connected in series give you 9pF, plus stray capacitances) will give you good results when the crystal is intended ie. for 6pF, though.
The values I show in my circuit are what worked for me. Like the link says, you can try R1=20M, r2=500K and caps between 10 and 20 pF.
I may have had a stubborn crystal, hence the 330K I used, and it's the only thing that really concerns me as these watch crystals do not like too much drive. However, if it shatters or ages too much, I'll try a new crystal with 500K but will keep everything else the same.