will be able to answer 2,3,and 4
first up if you use a 'primer' coat it makes your top coats "stick" better a good and reasonable primer is halfords acrylic grey primer it doesn't have to be red although some people prefer the red as it was a copy of what the original used and if your gonna do the"paint chip" effect this shows up nicely underneath

depends on what you want to do and what effect your going for
as to the putty i use Blutack no real preference it's just what was about and does a real good job but only for spraying if you hand paint camo start of by "laying" out the pattern in pencil (rubs out nice if you make a mistake

painting metal should be the same as plastic as long as you use a suitable primer (thats why i stick with the halfords primer) you can use tamiya primer if you want but for me there is no real noticeable difference

for tips on weathering and spraying type in "weathering and spraying tips" on youtube sit back and enjoy

you won't get a good job from the start and it will take time A good tip is if you dont want to mess up do a trial run on something else first that you dont mind spraying/ painting at least 20 times

theirs never an easy way to explain this but remember to have fun and so long as your happy with it thats all that matters

here's my 1/25 jagdpanther that i sprayed using the blutack method

Rob