Having just completed Marmaris to Lavrion, I can say Zai's route was a good suggestion. We modified a little due to prevailing weather and for our trip the meltemi was relentless, blowing F5+ every day and on two days F6/7.
Typically blowing from North although shifting NW.
From Kos, routing was
Kalimnos - easy enough first day
Levitha- fantastic anchorage, also with mooring
buoys and you have to visit the unbeliveable "restaurant" at the small farmstead.
Amorgos - strong winds and seas of the NW tip. Small harbour at Ay Annas.
Skhinousa - small anchorage S of Mirsini - shelter from meltemi and good holding
Paros - strong winds between Naxos and Paros. Great anchorage on Paros at Ormos Ay Ioannou. Popular but lots of space.
Sifnos - we could just sail/motor to Fikiadha which although massively gusty does give a good rest from the weather and allows for a route to
Kithnos - we tried for Loutra but with the meltemi blowing 30kts + the seas in the bay made the approach dangerous in my view and we took an extra 2 hrs to pass north and to the west on Kithnos to an picturesque anchorage at Fikiadha with good holding ( Kolona alos looked good nearby)
Lavrion - was a bit of a slog to windward and if we had had the time we might have broken the trip and stopped on Kea.
I hope this helps others and thanks again to the advise others provided.
ps Bit dissappointed with Olympic Marine
at Lavrion - a ghost town., no mini market and restaurant staff less than welcoming. Any other suggestions welcome.