If you want to consume large countries in one go, occupy them completely, take all you can in a warscore, instantly redeclare war and then go for it some more.
Yes, you're breaking truce and you might not have a CB, but balance that against waiting 5 years.
Alternatively, if the total war score required is between 101% and 200%, then wait 5 years. After 5 years of occupation the required war score for each province (and therefor annexation/vassilisation) will drop to a maximum of 50% of its original value over several years. A good way to get Switzerland as a vassal.
Yes, you're breaking truce and you might not have a CB, but balance that against waiting 5 years.
Alternatively, if the total war score required is between 101% and 200%, then wait 5 years. After 5 years of occupation the required war score for each province (and therefor annexation/vassilisation) will drop to a maximum of 50% of its original value over several years. A good way to get Switzerland as a vassal.