I am just getting into revisionism so I'm not sure about the various strains of thought in this subject, but from what I've gathered there are two main ones.
#1 is the idea that it is a misinformation campaign, which started during the war from isolated and scant reporting about genocidal crimes. After the war this continued, Jews and influenced governments could see that sanctification of such a myth could greatly further the ZIonist project. As such they worked to disseminate propaganda supporting the idea of genocide and put on show trials of "Nazi criminals".
After the state of Israel's formation, though the holocaust cult still had not achieved enormous prominence in the US and Europe, I imagine that Jewish power was already asserting tremendous pressure against skeptics. It would be useful to create a historiography of this. This pressure alone was enough to get not only the public, but also historians, many German speaking, to buy into the myth completely, despite the "overwhelmingly flawed" evidence supporting the theory.
#2 is the idea there is a vast Jewish program that is fabricating extremely convincing evidence and/or paying off/blackmailing "witnesses" and historians
this idea may be less popular among this group, but it is one I am sympathetic to. I imagine that the uneducated masses could easily fall victim to a simple propaganda campaign, as they have so often throughout history, but what about the experts? These are trained historians, who have to pass through a university system that preaches rigorous, well sourced historical analysis of all periods. These historians work with primary documents, their analysis is what forms the basis of most popular history books.
So in essence you have many WW2 German historians basically living in the archives, going through mountains of papers kept by Germans during the war, which include orders, meeting transcripts, correspondences, situation reports from lower level officers, as well as diaries and personal letters to family members.
To give you an inside look into this process, there is a rather incredible book called The Good Old Days that in particular has a lot of accounts of Nazi "genocidal intent" in the occupied eastern territories. For example in one section a Nazi commander tries making desperate appeals to spare the lives or delay the removal of skilled Jewish mechanics whose work is vital to the Reich's military interests, however the Germans are under orders to liquidate all Jews pg 174. There are many such examples in this book, as well as more "mundane" accounts of the cold blooded murder of Jewish women and children.
Every historian that I know of that speaks German and has access to the primary source archives, is a believer that at least there was genocidal intent by the Germans at least up until 42/43. Even David Irving has said 4 million Jews died, and does not doubt that terrible, unspeakable things happened in the East. Here he is discussing a passage taken from what he claims to be Eichman's private journals about the Einsatzgruppen.
Eichmann himself -- and I wasn't surprised to find it in his papers -- actually witnessed this. He went to see one at Minsk, and being a proper SS officer he went right to the front to make sure that everything was being carried out. He got so close, in fact, that he saw with his very own eyes how the victims were being made to go into the pits and stand there waiting to be shot. (We've all heard these descriptions of it, and I've seen some terrible descriptions from sources that I find credible.) He says he saw that one woman was holding a little child in her arms, petrified, and she held the child out to him, and he writes in his memoirs: "I was a parent too, and I instinctively stepped forward as though to take the child. But at that very moment the salvo of shots rang out. Both were killed only a few feet away from me. The child's brains were spattered over my leather greatcoat, and my driver had to clean the mess off."
So even a man like Irving, certainly no friend of the Jews, whose career and fortune and life has been wrecked by Jews, does not doubt all of these documents (when he says "sources that I find credible).
Clearly there is foul play afoot, but what exactly ?
The only reasonable explanation I can think of is either he is being payed off or blackmailed, or the primary documents are just that convincing, which in my mind only evinces the sophistication, power, illegality and secrecy of the group that is behind all of this. If this is indeed true, revisionists should not be disheartened, for if this "conspiracy" can be traced, if there is money trail or paper trail that they have left behind, then they can be fully exposed and the world may know once and for all who or what was really behind many of the greatest calamities of the 20th and 21st centuries.
if #1 is true, this is just a misinformation campaign and there is no new evidence or revelations to be revealed, revisionists are in trouble. There has been little success in mainstreaming revisionist views over the last 40 years, why should anything but the same be expected?
If #2 is closer to the truth, in my mind, revisionists should work to expose the "conspiracy" by secretly contacting sympathetic German historians who may be afraid to publicly speak the truth, tracing the genesis of all these fabricated primary documents through rigorous journalistic practice, and compiling a massive dossier to be unleashed on the world in one fell swoop.