i have done a fair bit of m's in various colors over the years. IF you are going to paint it - strip it down to brass as the nickel coat is very thin and if there are any microholes in it - it starts blistering quickly.
As with any paint - perp-work is 90% of the success. Clean, and clean again - preferably with ultra-sound jewellery cleaning kit. Once you "levelled" the surface - block sanding to smooth it and cleaned it again, primer coat it - preferably in a tint that is close to the color you intend to paint it. Give it a light coat of primer, block sand again to find the high spots. Give it another coat of primer and let it dry. Use whatever paint you are going to use - light touch - not to thick and "bake" for 30 min # 125 C. Once the 30 minutes are up - resist taking it out - turn off the oven and let it cool down. You can "shock" the paint if you take it out too soon.
With the first coat on, clean out engravings with a tooth pick. Check for uneven paint - overspray etc - clean and put on the second coat - again "bake" for 30 min #125C and let cool. If you want a really nice finish - clean out the engravings and white fill - then run a very light clear coat over it all.
When stripping the camera, remember that the screws holding the self-timer and frame selector are not brass, they are plated steel and the acid strip will destroy them!
You can get a electro plater to run a reverse plating on the brass parts - less harmful than the acid strip and it takes out the nickel too. Worth the cost.
Be careful when removing the windows - they are held in with fragile brass clips and the break easily.
I have done M's in Hammer tone and in black - and Shintaro and I have done them in blue/grey, in Ivory white, crackle finish black, deep purple ( powder coat - dont recommend it as it builds up and you spend days cleaning edges and threads.
I saw a very slick M2 in Tokyo last year, deep Royal Blue, gold filled engravings and midnight blue (dark) covering. Far less garish than it sounds!
Be prepared to make several attempts before you get it right! Thats why they have paint-strippers!
If you know some-one in the bike customizing business - they are a wealth of information as to what paints to use and how to apply it.
Good luck - and the pizza's warmed in the oven will only taste of paint for a couple of days.