I have been doing this for thirty years. I use Heritage Family Tree and it is creaking at 3308 individuals entered. Of course, I do have a lot of sources.
Our library allows us home access via the internet to Heritage Quest microfilms of the Censuses. Also I have visited the National Archives in Sand Point near Seattle. I am also able to search newspapers through newspaper archive. This is great for infomation on persons later than 1930, the last census year released. In 2012, the 1940 census should be released.
The most helpful census is the 1900 because it lists the month and year of each person's birth. Also the number of children and number living for each wife.
Of course you have to know something about the families, where they lived and the names of the family members.
Computers are wonderful for this. I was missing one family in the 1910 census, so I searched the whole country instead of just Wisconsin. It turned out they were living in St Louis during the 1910 census.
A charter member of the Buffalo Plaid Brigade!
Whether you think you can or think you can't, you're right.