I thought I understood but it does not look like. When I choose spy to research I am given a choice of provinces with highers techs where I can spy. Now no provinces are available for me because there is no province more developed then mine. Marshal and accountant (forgot how he is called) can "spread" technology only in my own demesnes. How can they spread in their own demesne especially when it is already the most developed? The priest on the other hand can spread technology (culture) in any provinces of the world. How, can it be?
Your tech development in the tech screen is only for your capital county, not for the rest of your demesne, so you can use the councillors to spread it into the other demesne counties.
Look at the single tech specific map (click the box left to each tech and watch the map), also hover your mouse over the tech numbers in the province/county view.
It wil show the percentage of probable increase in tech for that specific county.
The priest spreading everywhere issue is a misunderstanding.
Its' pretty simple:
Priest, steward and marshall spread tech into each county (where they are doing spread research) of your demesne from your capital or into your capital county while a spymaster steals tech somewhere from that more advanced county.
Spymaster spreads tech from a foreign more advanced county to your capital.
Temples and universities increase spread to this county in which they are build.
Tech points are aquired by your own characters skills and buildings. Military tech points only through skills and battles.
Tech points, thus actual resarch, can only be done by dukes and upwards.