JHB Have taken photos of the same piece of timber at various stages of painting and weathering,all based on Martyn Welch's book
1 is obvious! 2 is painted with Sleeper Grime (in this case Railmatch) 3 is top coat added (Revell 64) but add your chosen colour!
4 is after rubbing with a carbon fibre brush 5 is after dry brushing and rubbing in with finger (Humbrol 64 Grey pus a touch of Humbrol 24 Yellow)
6 and 7 after weathering with powders (Greys and Dust colours-just add gradually and not too much) you will know when it looks right.
8 is an experiment -wood painted as per the book (mix of Humbrol 64,110,29 plus a touch of 33 and 53) After dry brush sparingly
with Sleeper Grime.Hope this is useful.