I don't think one has much choice, other than using all the railcapacity for factories.
I followed Sillyflower's AAR against Brian. Brian lost : Leningrad, Moscow, Kolomna, Kursk, Rostov, Stalino, Kharkov, Voroshilovgrad and everything west from that.
I noted the dates at which cities were lost, put that next to the railcapacity and the factories needing evacuation, and came to the inescapable conclusion that you need all the railcapacity just to evacuate the utmost necessary industry.
If done properly,one will be left with 200 HI, 300 AP, a loss of around 30 vehicle factories (that's just around 5 % of your vehicle production), half of the tank and il-2 and half of the mig 3 (which turn into Il-2). All the Li-2, and for the rest just 1 pnt of each plane factory.)
One could also opt for 1 Li-2 pnt, 1 KV-1 pnt, and 1 T-34 pnt from kharkov, enabling the evacuation of pretty much all the vehicle factories as well.
You just need all your rail capacity for that, leaving the cumbersome task of moving all the units by road. A lot of work, but it is managable.
More ground will probably be lost this way, but saving the industry has the highest priority, and pretty much all one can do against superstrong GHC players.