I'd pop into somewhere like B&Q, Wilkos, Halfords, etc and pick up some plastikote spray rather than
GW's spray - about half the cost for twice as much. You can look at other brands of automotive spray primer as well as they come in many different colours and will generally give you a good base-coat and of an appropriate colour (in your case red would probably be pretty good

).
I'd then get a black wash, sepia wash and a mid-silver paint, a fine detail brush (forget the drybrush) and a small plastic pot for water (I use an egg cup but whatever works for you

).
I would also pick up some double sided tape or some blutac.
So, spray your soldiers with your red primer - I stick them onto a strip of thick card in single file (so you can spray up at them from underneath more easily to ensure they are entirely covered) using the double sided tape or blutac to hold them in place. Ensure you shake the can well for at least a minute if not more, and check the nozzle isn't making it spray badly by doing a couple of test bursts on something like a bit of card or paper.
Leave this to dry for a couple of hours or overnight if possible. Also leave it somewhere well ventilated if possible as it will smell quite a lot.
Do a very heavy wash or two of black wash over the areas you want to be black. This should give you a nice dark black with a hint of red shining through and also automatically give you shadows and highlights without having to highlight up from a flat black.
Once dry, paint the bits you want brass coloured with the silver, allow to dry then hit with a mid (slightly watered down) black wash, then when dry use the sepia wash to turn it a golden brass colour. Alternatively use something like dwarf bronze (sorry, I don't know what the new colour name is) with a light black wash over the top.
Then hit the red areas with a light black wash to give them some shading.
Pick out any other details in whatever colours or ways you want.