Hi Harry. As with everything, there are those that do and those that dont! Nothing is wrong in the world of modelling. There are giys who build unbelievable models in my local IPMS club, but never weather. They are interested in the actual vehicle. Then there are those who WEATHER! Im probably one of the later! At the end of the day the choice is yours.
I think you have achieved so much, so far. Excellent building and painting. The colours look nice and flat, Etc, etc. But I feel if you want your vehicles clean, keep them clean. if you chose to weather them, do so! But both dont go together.
This looks great, but the tracks seem weathered or dirty at the bottom and then clean or unweathered at the top. This would be my hint at improving your skills. But you are definately on the right track _( no pun intended). There alos seems to be spots inside the wheels that are not painted. These might need some touching up. Good luck with the rest.