i do blackouts all the time. leave the filter and heater going etc, you wouldnt want to turn them off. all you do is stop any light getting to the tank. just feed the fish once or twice in that time and itl be fine.
spot dosing is basically getting a syringe and squirting one or two ml on the affected area. (normally it is 1ml for 50L) on my 120L becuase it has alot of plants i dose about 4 or 5 ml so it doesnt matter if you go over. repeat the process for 0one or two days and the algae should go a funny colour and then dies. the BBA that i had went blue and red and purple, all kinds of colours before dying out. however if you have alage on any mosses, glosso or HC dont spot dose as it also kills the plant i believe. but i doubt you do as you have cichlids.