Removing everyting with the wire brush is even nicer.
When I bought the rust prevention greases I imported them from Germany. I did a lot research on rust preventive materials, because of my old Saab. Mike Sander really excels in the long run, but for bicycle use FluidFilm has the more convenient products, like for example Gel grease and AS-R oil in in aerosol can with several nozzles. I do not know about availability in Portugal. However everything greasy has good anti rust qualities, so I wouldn't worry too much. There even is no real need to remove all rust. Simply on top. Dito for inside frame.