Yo Paul !
The first pic is a Tamiya Chally 2
The next is a Danish Leo 2A5 Tamiya/HobbyBoss being masked before adding the texture.
Next two show the final result on this one.
Then there is a Tamiya German Leo 2A5 already airbrushed, as you see you'll have to look real close to notice anything. Just like the real thing!
The last one is a Tamiya 2A6 with Perfect Scale engine and with Pro Art Model side skirts slightly weathered, so you can make out the anti-slip areas.
With the Leo 2's I sand down the existing surface to get the blank rims after the texture has been applied, this is a very distinctive feature (especially when wet) on the real Tanks.
I use a Badger 150 airbrush at high pressure with a medium size needle.
Then I mix MR SURFACE 500 or 1000 with a little turpentine or so and start spraying the masked areas.
Mr Surface has a tendency to dry rather fast, so all I do is keep deluting what every is left in the airbrush until I would have to add some more MR SURFACE.
At this point I just add turpentine to spray out all contents and to clean the nozzle when I reach the end of each filling.
Then I start all over again.
MR SURFACE has the tendency to "smoothen" a bit while drying, so sometimes I have to repeat this procedure once more after the first layer is set to bring it up to strength.
The Surface of a Leclerc would be rougher, so I mask everything as usual, mix Tamiya Putty with liquid glue, dip a old brim paintbrush into it and then "tap" the surface with it.
After that I spray an extra layer (as described above) over that area and the result is a not too, but visibly more rough of a coating.
Hope I have been able to help U!