zippers

I have a well used hiace that has some rust bubbles along the roof gutters nothing that looks to bad but need to know what to use to kill it so i can repair without pulling out rooflining if possible as im guessing it will be worse inside the roof .Done around windscreen with soda blasting then killrust and it worked dont know if i can do the sides this way or just do it from outside ?

Any help will be appreciated .....

Super extra spacia with 88.000 km auto 2lt gets looked after but no matter what i do gets real bad fuel milege ,new filters oil changed only get 310km from 40 lt tank?