cycling from Sofia into Northern Greece and onto south

Hello,
my wife and I are now in Sofia after cycling down from Poland.Hoping to head south now to north Greece and then to south or maybe island hopping.
We would appreciate any advice and roads,trafiic conditions,wild camping and official sites that are open all year, reccommendations for cheapish hostals or longer term apartment rentals, and maybe animal rescue centres that may have volenteeer work for free accomodation.
Thanks for any thoughts,ideas advice,
happy cycling
jim and terhi fullwood.