Why don't you mask off the white areas, leaving just your painted areas exposed, and then hit those with a gloss or semi gloss clear coat. Once dry, mask those areas off and then polish the helmet? You can also not clear coat your painted areas if they are fine. Just mask them off to protect them. I'd mask off the tube stripes too (just single tape covering the area, not each individual stripe).
As to polishing, concentrate on the "high" areas of the helmet (dome, tubes, cheeks, etc.).
And then, don't forget, POST PICTURES! I'm working on my first build now as well so I for one wanna see 'em.