I have yet to try this out, but thinking about the China situation I think this would be delay Japan enough to get China going.
1941:
On R1 move all ERuss inf to Buryatia (manuchia border) giving a total of 7 inf on the boarder, move Moscow tank east and purchase 1 fighter on R1. Move Yakut inf east. Inf in Eve N Okr and Novo head to China west most territory.
So at the end of R1 there are 7 inf on manchuria boarder, making Japan think twice about an IC in Manchuria. They could still put it in Shanghi, but then can only produce 2 unit/turn instead of 3. Also
if Japan wants to attack that stack they will need to bring a sizeable force to destroy it, thereby diverting units from other more importatn J1 attacks. By leaving Soviet Far East open for invasion I am enticing Japan to go that way and waste time taking only 1 IPC per turn and drawing forces away from China.
On R3 attack Manchuria with 8 inf 1 tank (from moscow), 1 fighter (from R1 buy). Depending on the Japan force in Manchuria it should be easy to take. If a sizeable Japan force is in Manchuria then I would just hold the ground.
By having two sizeable russian forces on both sides of china it makes Japan work harder to take china, thereby delaying their advance into china.