To be honest I would think twice about doing it,lots have had trouble with it not sticking and coming off in lumps,if its rust in the tank that is the problem the best way is to have it dropped in a cemical bath and fully striped,it will take the paint as well.Your choice of corse.I have had problems with Creme but I hear there is another product that is 3 steps,dont
remember the name but the first part strips and cleans,ect ect
I think they sell it in the back of Classic Bike Mag.Good Luck.
Just read your post again and it said you had the part a and b
so maybe its the improved kit?Main thing is to get it clean,
have you tried the nuts and bolts in the tank with petrol and give it a shack,knocks off any loose rust,when the product is in the tank keep turning it so you get a light cover and it does not go hard in lumps.