They were brought up in a thread here some time back, and also in several books. They recieved about 6 months training. The website is now defunct, but here is an excerpt:
The Night Witches
In 1942 the Soviet Union formed three regiments of women combat pilots. The 586th Fighter (IAP) Regiment (Yak-1s and later Yak-7Bs), the 587th Day Bomber Regiment (Petylakov PE-2s) and the 588th Night Bomber Regiment (Polikarpov Po-2s). The 'Night Witches' were the women of the 588th Night Bomber Regiment. All of the mechanics and ordnance loaders of this regiment, as in the 586th Fighter (IAP) and the 587th DayBomber Regiment, were also women.
Trained for six months at the town of Engels on the River Volga near Stalingrad, they flew obsolete Polikarpov Po-2 biplanes, that were otherwise used as trainers. Generally unarmed they carried a variety of droppable ordnance consisting of bombs/grenades (even Molotov Cocktails) thrown from the aircraft by the observer, and on later aircraft, underwing racks for up to 264 lbs (120 kg) of bombs or four RS-82 rockets. Like most Night Bomber Regiments, they were nuisance raiders with targets usually of little strategic importance, but the psychological effect of the terror raids had a major effect on the Germans who soon gave the women pilots the nickname of Nachthexen or Night Witches, presumably because of the fact that they were women and flew wooden aircraft at night.
Because of the aircraft's wooden frame and fabric covering contruction combined with the low heat signature of the small 100 hp (74.6 kW) engine, and flying very low to the ground, they were difficult (if not impossible) for radar equipped night fighters to detect them. Flying close to the target and then cutting their engines and gliding in to attack, also added to thier terrifying effect.
Harassment night bombing was very difficult to do, considering the low performance of the Po-2 biplanes was even less than most World War I fighters. Very slow, but it was also very maneuverable. When a German fighter tried to intercept it, the Russian plane could turn violently and nimbly at a speed much less than the pursuing fighters stalling speed, requiring that the German make a wide circle to come in for another pass. Then he was again met with the same evasive tactic, time after time, hoping that in frustration he would break off the attack altogether.
The Germans later devised a defence to their attacks, that the Russians later called a 'Flak Circus' wherein searchlights and flak guns encircled probable targets. The 'Night Witches' adopted a dangerous tactic in which, flying in formations of three aircraft, the first two aircraft would fly into the target drawing the searchlights and flak onto themselves and away from the third aircraft that would attack the target. After a successful attack they would regroup and switch places with each aircraft taking its turn as the bait.
The Soviet women bomber pilots earned in total 23 Hero of the Soviet Union medals and dozens of Orders of the Red Banner. Altogether, the Po-2 pilots flew more than 24,000 sorties and dropped 23,000 tons of bombs earning their place in history.
Can't get the link to come up on Wayback, but there is a link at Axis History Forum, if that helps; we're not supposed to link to other forums for some reason.
They were able to use old biplanes because the Allied bombing campaigns forced Hitler to strip the Eastern Front of planes and anti-aircraft gunnery, leaving the Soviets with almost total air superiority.