For unpainted PE parts do they get painted as they get put together or do you paint them after everything is glued together? For example I'm working on the side walls of the cockpit interior of Me-109.

It depends upon how many different colours are involved. For example, in the Bf-109 there are the oxygen regulator, the trim wheels, and the fuel pipe which all have different colours from the main cockpit colour. I'd probably leave those off for detail painting, but glue together everything else that's going to be painted all at once.

Also, if there's a detail colour that may be obscured by another part, I'd likely leave that other part off until after painting.

Seatbelts I paint off the seat, just because I tend to go overboard whenever I'm painting seatbelts on the seat; avoid messy traps whenever possible

Thanks! This is my first time using PE and there is definitely a sharp learning curve!

First paint the components with Mr Hobby Mr Metal Primer. It is a clear lacquer that looks and smells like nail varnish. It dries extremely thin and you cannot tell it is there but it makes a major difference to the adhesion of paint, which will no longer readily chip off.

I hand brush my PE parts, either on the fret or the model, with Rustoleum paint from a can thinned with acetone. Any color will work and it's very strong and durable.

I wish this was much easier to obtain in Southern Ontario

Ask hardware stores and DIY centres if they have metal lacquer. It is a clear lacquer used to protect brass or silverware from tarnishing. In the UK a company called Rustins markets it but you have to search it out, not every retailer stocks it. I am sure it is the same or very similar to Mr Metal Primer.

http://www.rustins.eu/Results1.asp?Keyword=clear+lacquer&Submit2=Search

Something you could try which should be easily available is the clear lacquer used to protect alloy wheels or sprayed over metallic finishes on cars. Again I think it is very similar to Mr Metal Primer. You should be able to get it either in an aerosol can or a tube of touch up paint. In both cases I think you will probably need to thin it even more with acetone.