One of the few things I never really got into was weathering, I tried it on a truck model, using model paint, never really liked it, never got a good mud pattern.
Forward to the present day, one of the members at www.cardmodels.net showed one of his little tricks, He showed off a weathering set from Tamiya, check it here.
I have picked up all 4 sets, only 3 were shown in the thread above, the fourth set has burnt blue, for burnt metal, like header pipes and exhausts, and the Oil Stain, for leaking oil from vehicles or aircraft, there is also a burnt red for rust colored burnt metal
I picked up my sets from Hobbylinc
I will try to use them in the future, on some of the more simple models, from Racepaper.de to see if what works, I'll keep you posted.