I went down to Turkey last year on my own, from UK. I took the direct motorway route, through Germany, Slovenia, Croatia, Serbia, Bulgaria (my 3rd night was in Sofia). The next day I was at the Turkey border by 13:00. It took me about 1 hour to get through the border including getting a visa and getting the bike x-rayed. Your papers are checked many times!
The other borders were easy, one police guy asked if I had in my camelback. Oh on the Bulgarian border after clearing all the paperwork a big dog decided to bite my boot as I rode off but he could not keep up with a 1200GS.

I stayed in Istanbul a couple of days and then rode down to Cappadocia (where I camped) and then to the Eufrates river, and then back along the south coast. Generally riding was easy in Turkey, a litle busy in the towns but no problem, but Istanbul is very busy and drivers were impatient, no fun. I stayed in small hotels which were cheap outside Istanbul. After Turkey I came into Greece by road and again the border was easy, and later I took a ferry back to Italy.

However from travelling around the Balkans on earlier trips you will need to get insurance(green card) at the border of Montenegro and Bosnia. For Turkey I got a green card before I left for Uk. I believe I also got a translation of my driving lisence.

As for distances, I was doing just over 500 miles per day down to Sofia. In Turkey where the roads were of a mixed standard, then 250 - 350 was more normal. I took 20 days for the total trip for just unded 6,000 miles or 10,000km.

If interested, and sitting comfortable you could scan my trip report on another site - Candover Valley UK to Euphrates Valley Turkey - Updated with pictures.

Hope this info is some help. Enjoy your trip.