I need advice on the sequence for building the above ive only tried it once and it was a case of now what i need to know is when do you paint the track and wheels, before you build or after,after seems a little awkward as im working in 1/72.I would be glad of some advice.

When using 'link and length' or individual link tracks I always paint afterwards. I tried painting the wheels and track first, but then had adhesion problems when the weathering was applied later.
Painting afterwards is fiddly to say the least, but avoids other problems.

Thanks for the answer Dave I did mean lenght and link to much as usual. I was thinking of painting first but leaving a clear glueing spot top and bottom then touching in afterwards, them tyres are so fiddly.