After studying photos in the Australian Railway History Oct 2011 volume 62 number 888 in which these wagons appear in quite reasonable condition I decided to weather them as follows.The only difference between the Eureka and Austrains wagons is the Austrains GSV chassis unclips from the body as the CW wagon.
1 Carefully remove the buffers and the body will lift off the chassis.
2 Remove the floor from the chassis via screws at either end.
3 Unclip the roof from the body.
4 The couplers and bogies are next to be removed.After dismantling the wagon, mask where the writing is along the side of the chassis and on the body where the wagon code is. I used narrow Tamiya masking tape. Then spray a thinned coat of black etch primer over the entire body so that the weathering paint has something to key to, now remove the masking tape. Floquil grime is next and then mud, remember to take your time and make sure the paint is very diluted, practise before spraying the wagon with an uneven light spray inside and out so not to get the paint too uniform. If you think that there is too much of a colour tone it down with thinned grimy black. Pastel chalks can be used to enhance the weathering further. Finally a spray of Testors dulcote with a dash of matt black will take any shine off and tone down the finish.