I would've loved to have seen a leader class DotM Megs, if you ever do create one I'd be very interested to see it!
Regarding the paints, I just use the small pots of Revell or Humbrol and apply the paint by brush. This particular figure was too intricate to mask off and spraypaint in my opinion.
There's a lot of techniques that I've read up on and used like dry brushing, sponging and using thinners.
Most of this guy is painted, the worn metal look was created by doing a black undercoat on the parts I wanted to paint metallic, followed by a drybrush of Steel and then a lighter drybrush of silver to highlight the edges and create a more tarnished look on flat surfaces.
The rust was a bit harder, I started by applying thinned rust colour using a fine brush to the areas I wanted to rust up and also areas to produce the effect of the rust running down the paintwork, then used a small sponge (you can get these from art shops, basically just a stick with a bit of light sponge on the end) to dab on a few light highlights of copper then silver to produce the effect of recently exposed metallic areas, then went sponged over these with an ever so slightly heavier coat of the rust colour again.
I then thinned down some black (quite a bit) and got a larger brush, dried off some of the thinner then went over the whole model to give it a more worn and dirty look.
It sounds like a lot of work but patience is the key. I'm still very new to model painting, this is only my 4th attempt at it. I did a lot of reading and watched some youtube demo vids before attempting it myself. I still think it's very amateur compared to some of the repaints I've seen however it's very satisfying when your model turns out even remotely like you had hoped.
Here's some of my earlier attempts:
DotM Deluxe Roadbuster:
http://www.otca.com.au/boards/showthread.php?t=11948
Dual Model Kit Bumblebee:
http://www.otca.com.au/boards/showthread.php?t=12059
DotM Sentinel Prime (very minor and basic repaint in comparison to the first two).
http://www.otca.com.au/boards/showthread.php?t=14291
The most important thing I think is to enjoy what you are doing and not be afraid to have a go. I attempted the drybrush and sponging techniques on one of the legends class figures first in case I messed up and was no good at it. Surprisingly it turned out quite well and wasn't that difficult.
I look forward to seeing how you go, if someone as inexperienced and bad at art as I am can make a figure look even halfway decent then no doubt yours will turn out amazing.