I have just finished painting up some 4Ground Wagons and a Water Cart.
I really like these but kept thinking to myself that they are too big. However my only previous experience with wagons have been with an Old Glory Stage Coach and some Wagons scratch built using Hinchcliffe Cannon wheels. So maybe they were smaller because of the era that they are from when models were 25mm tall.
The general purpose Wagon was painted first using a colour mixed from a Vallejo Grey with some Blue added to it. I used far more than I was happy with and had to keep mixing up more and more paint to cover them plus the Water Wagon and stand. With the Boer Wagons I decided to use a different approach and went and bought some Art store paint. This was quite a bit easier to work with and was easily thinned. I was not sure of the Colour of these wagons so enquired on TMP, where we did not really get a consensus of the correct Colour. However it was pointed out that an Osprey has a wagon painted Green and Red which was what I found when Googling for images. I am still not sure if this is a modern idea of what the Colour should be. I did find an advert for another type of wagon which was sold in a standard Colour scheme. Unfortunately I did not save the image. The Green has been highlighted with a lighter Green and I first put a Devlan Mud wash in the corners which I could not see so put a wash of Agrax Earthshade which is not really evident either. The metalwork on the wheels were first painted a really dark brown and then I tried to paint Oily Steel over the top. I did not like the look so repainted the wheels (only the Water Cart fortunately) and then rubbed a Lead pencil over them which I like as it is quite subtle. I was not sure if the barrels should be painted or left plain. I assumed that they would use any old barrel to hand.