A In general it is better to do Tikunim consecutive so the Klipot have no chance to recover. In Kitvay Ari it rarely mentions the word consecutive. However by the Tikun of Pay Daled tanasim he says that it should be done consecutive.
Doing the fasts consecutively is much harder and many of the latter Kabbalists agree that it is not necessary to do them consecutively in later generations. If someone does do it consecutively it will surely be even more effective.
There are also shortcuts, the Ari writes that a 2 day fasts counts as 27 fasts and a 3day as 40. The only thing is these can not be broken up for different Tikunim and must be used for the same Tikun.
The Chida brings down how to do the 84 fasts consecutively during SHOVAVIM and many Kabbalists do so. You use Shabbat and Rosh Chodesh to break up the fasts since they are not counted as breaks.
Q Should regular fast days (Taanit Esther, Asarat Btevet ETC) be counted as part of the 84 fasts?
A No regular fast should not be counted as part of the number.
Q If someone forgets to accept the fast during the Amidah of Minchah on the day before, can he verbally accept that the next day should be a fast day for him in any language?
A One can accept the fast in any language. If he forgets to do so during Mincha he may accept the fast until sunset.
Q Can one accept on himself a fastday for Sunday on Shabat - Meaning can he declare on Shabat that Sunday will be a fast day for him?
A If a person wishes to fast on sunday he may accept the fast during Shabbat afternoon.