No need to visit an archive or even go to school! You can practice these steps in the privacy of your own home or Fuehrerbunker.
1. Always say the grave site is too small or too large, whilst ignoring the blatant contradiction between these two positions.
2. Call your opponent a "Jew bitch", "Jew lie" or "Judeo-supremacist", whilst insisting that there's no such thing as antisemitism.
3. Ignore the fact that Jewish religious laws have prohibitions against the disturbance of human remains. Demand full autopsies that would contravene these laws.
4. Pretend that partial excavations or test drillings were full site investigations and judge the results against that benchmark.
5. When referred to translations of Polish or Soviet postwar reports of mass grave excavations, bluntly dismiss them saying that those 'Communists' were liars who cannot be trusted. When shown evidence independent of those 'Communists' that corroborates their findings, ignore the argument or argue as per item 7.
6. Pretend that only those parts of an excavation that are published on-line were actually carried out. If it's not on-line, it doesn't exist! Forget that this would rule out nearly all historical studies of mass killings or criminal cases ever conducted.
7. Insist that German wartime documents and perpetrator eyewitnesses do not constitute real evidence, without explaining why.
8. Insist that if every victim cannot be identified by name, or if victim estimates change over time, this proves that the killings did not occur. Ignore this rule when discussing the firebombing of Dresden or crimes against ethnic Germans in Eastern Europe.
9. Keep demanding to be shown 'just one' sample of a bone fragment, tooth or other type of human remains. When asked about the relevance of your demand, ignore the question and repeat the demand. When shown photographs of human remains found at a Nazi mass killing site, yell that it has not been proven that these are actually a) human remains and b) Jewish human remains. Alternatively, argue that such remains could have been brought there from the local cemetery.
10. Apply the "falsus in uno, falsus in omnibus" fallacy to any source (e.g. eyewitness accounts given to Father Desbois), without reference to any established legal or historiographical rules that would justify such a negationist approach to the evidence.