Working on CONvergence stuff, eh? So am I!
Bubble helmet: A few friends and I are doing a group costume, 50s-era sci-fi spacesuits. The helmets are made from a 14" plastic globe for outdoor lights: http://www.1000bulbs.com/product/7570/3202-14020-003.html
. A collar piece is built up around it, with fans front and back. The suit is a modified mechanic's speedsuit, with custom-embroidered patches. Preview pics here: http://www.flickr.com/photos/danbackslide/sets/72157626919911758/
Squirt gun painting: My brother and I have steampunked a fair number of Nerf guns; the Maverick in particular is cheap and cool-looking (like a giant revolver). I like to disassemble the gun before painting, but my brother usually leaves them assembled. Start by giving the gun a light sanding, just enough to break up the surface a bit. Then spray the whole body with flat black paint for plastic, which will give a base for other paints to stick to. From there, imagination is your guide... A pic of my brother's work on a Nerf rifle: http://greasedupdeafguy.deviantart.com/gallery/#/d3e07by