Seal or no seal? Black wash?

I just finished my helmet paint up and now I'm wondering if I should avoid sealing all together or if i should seal it with a dull clear coat?...but with that I'm worried it will take away from the shiny metal like apparance of the dent and other silver damage...?

I also read about giving it a black wash which is apparently mixing black acrylic paint with windshield washer fluid and giving a good spray down leaving a weathered dirty effect....anyone got any views on this? Any help?

I have not finished my helmet, so I would wait for the real experts to chime in. I say always coat it for protection. I made tons of plastic models years ago, and those are not handled as much as a helmet. The paint on my models can come off if handled a lot, so I always coat with dull. I believe the same concept can be applied to the helmet.
I'm in the middle of painting my helmet, and I plan on dull coating it when finished. I'd rather not repaint it if the paint accidentally gets rubbed off somehow? haha... I will be airbrushing with acrylics, so I really need to dull coat it. Maybe dull coat around the silver and the dent, and then gloss coat them?

also, I am going to dry to do a wash, but I will use a brush for that.
I refer to superjedi's painting threads, and he's very experienced and talented.

Rogue Studios felt that this method helped to blend the colours in nicely as per his paint list thread. I've not done it myself but can test it out on a helmet that I'm not fussed about if it helps people although you'll have to wait a few days. In fairness Rogue Studios did a heck of a lot of work on painting helmets and developing his colour list; his list is the basis for a lot of what now happens so if he recommends it I'd say go with it. Personally I wouldn't use a dull coat or clear coat as I feel that both acrylic and enamel are quite hard wearing once dry.
http://www.thedentedhelmet.com/f23/rogue-studios-esb-color-list-painting-techniques-3630/

Thank you..that's very helpful..I was leaning more towards not sealing it at all because I also used acrylic paints and figured it wouldnt rub off so easily and also i don't wanna risk ruining all my hard work lol...as far as the black wash is it ok to do without a clearcoat?..If anyone's done this post pics of ur results please..

Here is mine, unsealed with a blackwash




This is a trooping pic, I would have to search for an indoor pic of just the helmet.