The USSR never had to resort to such desperate measures as recruiting militias of teenagers and grandpas like Germany was forced to do with its Volkssturm.
Except for People's Militia and Partisans.
According to the training program adopted by Stavka in 1942, forming and training of an infantry division was supposed to take 780 hours (3 months). The schedule has always been fictitious, and in 1943 Stavka acknowledged this by reducing the number to 504 hours (2 months: 306 hours tactics, 100 hours shooting, 74 hours general, 24 hours politics). Training of individuals supposed to be sent to already existing units was scheduled to last 15 days for infantry and 30 days for divisional units (respectively 30 and 60 if an individual has not undergone the basic military training in the peacetime).
Please note that contrary to the British or German systems and alike the American system, in the Red Army there was no unit rotation. Divisions were not withdrawn from the front for rest, re-organisation or re-supply. Freshly recruited individuals were meeting their brothers in arms under the enemy fire. It does not take much to imagine how, under these circumstances, the company, platoon or batallion training looked like; and from 1943 onwards vast majority of those who ended up facing the Nazis were trained following an individual programme.
How did it work? Notorious shortages of everything made hardware-related training a mockery; like in case of the Americans, there are also accounts of commanders complaining about new soldiers unable to dismantle a gun. I know cases of 20-25% trainees not even leaving the barracks due to … lack of shoes. Under extreme pressure from the front the schedules were being trimmed or condensed; if in case of forming entire units the training somewhat resembled what it was supposed to be, in case of individuals it was often reduced to few days (if any). Oleg is quoting a sample of a protracted, 6-month long training of a single division. Surprising, though possible. But I think it does not take much effort to find divisions formed and sent to fight in less than a month.
So a huge pool of manpower is very, very nice. But what good is it with these standards.
I would be interested in the impact of targetting soviet industry faster, or limiting the lend-lease.