The white spots you see on the fish are a cyst and are not killed by the treatment, it is the next stage in the life cycle that can be treated hence the advice to wind the temperature up. This speeds up the life cycle and makes available the vulnerable free swimming stage to be killed. The fish is cured when all the spots have dropped off and been killed. There are a number of treatments available that work including malachite green/ acraflavine, copper sulphate, Furan 2 or many others available from the pet shop. Go by the instructions and treat until clear of spots. I find the best way is to observe the fish in the dark with a torch.