Tech sharing only worked in certain ways and between certain nations.
The Commonwealth shared just about everything. Canada and England were probably the closest, since Canada had the greatest ability to produce military equipment than any other Commonwealth nation. The other Commonwealth nations relied on British not only providing the tech, but the equipment as well.
Tech sharing between allies (i.e., nations that are working together during WW2) should be much more limited. What did Germany give to their allies that are representative of technology?
Most minor axis allies used domestic small arms and uniforms.
They primarily used domestic, domestically purchased, or second hand German heavy equipment (such as captured Allied tanks, small arms and aircraft that were of no use to the Germans).
The Western Allies were a bit better, they shared more information between one another, but there were also limitations there. England was not keen on giving away their Radar technology.
Things shared with Russia were basically things that Russia had already. Tanks sent over were either inferior or equal to Russian tanks, same with aircraft. This would be resource sharing rather than tech sharing.
Basically, a proper tech sharing should only consist of tech that may benefit a minor ally, but is nowhere near the top of the line equipment that the sharing nation has.
So, if Bulgaria has tankettes, Germany just developed Advanced Light Tanks, Germans could then share Basic Light Tanks with Bulgaria, but they would NEVER give them Advanced Light Tanks.
Also, tactics were rarely shared. The Germans developed Blitzkrieg, but did not share its secrets with their allies.
So, realistic tech sharing should exclude Doctrines, and it should never be top of the line technology (unless it is between the Commonwealth which did routinely share tech). The US and UK did share some tech, in a way (such as the UK using Shermans and the US using 6 pdr and 17 pdr AT guns), but it was fairly limited.
