In 1984, does the Party use brainwashing and torture to control the Proles? How does the Party ensure that the Proles do not improve their status?
In 1984, the Party does not use brainwashing and torture to control the Proles like it does to control Party members. In fact, what is interesting about the Party's relationship with the Proles is that, generally speaking, it leaves them completely free to live their own lives. The Proles are not monitored by telescreens, for example, and are not required to take part in Party activities, like the Two Minutes Hate or Physical Jerks.
As Winston points out, the Proles make up 85% of the population of Oceania. Considering their large numbers, the Party only deploys a few agents from the Thought Police to keep the Proles in check. These agents "spread false rumors" and remove the few individuals who are deemed dangerous, as Winston explains in Part One, Chapter Seven. Beyond that, the Proles are left to manage their own affairs and their lives tend the follow the same pattern:
They were born, they grew up in the gutters, they went to work at twelve, they passed through a brief blossoming-period of beauty and sexual desire, they married at twenty, they were middle-aged at thirty, they died, for the most part, at sixty. Heavy physical work, the care of home and children, petty quarrels with neighbours, films, football, beer, and above all, gambling, filled up the horizon of their minds.
It is this simple life which prevents the Proles from ever rising up and becoming a threat to the Party. As pointed out in Part Two, Chapter Nine, they are ignorant to the notion that they are strong enough to ever pose a real threat to the Party:
From the proletarians nothing is to be feared. Left to themselves, they will continue from generation to generation and from century to century, working, breeding, and dying, not only without any impulse to rebel, but without the power of grasping that the world could be other than it is.
The Proles are, therefore, happy and content as they are. They have no interest in ever improving their social status because the Party leaves them to live as they choose. The Party also allows them to have as much entertainment as they wish: music, gambling, alcohol, and pornography flood the Prole districts, ensuring that the Proles are kept permanently amused.
So, is it the Proles' ignorance which keeps them under control and which also prevents them from ever feeling the need to improve their station. In Winston's mind, access to education is the only thing which might give them the necessary awareness to rise up and rebel. But the Party has no intention of ever giving them that privilege.