Rough Texture

As explained by Tojo, Mr. Surfacer 500 is the best and easiest product to produce the cast texture you are looking for.

You can even make decent weld seams using two pieces of masking tape side by side then dabbing on a thick coat of Mr. Surfacer along the uncovered plastic. In a few minutes then remove both tapes revealing a weld line that is still soft so it can be tooled into rough uneven spots here and there just like the actual weld seams.

Here - try this: Get a half inch wide brush.  Put a rubber band close to the end of the bristles to keep them from splaying out. Use the end of the bristles to stipple primer over your model surface. Or use lacquer thinner very sparingly to soften the surface as this too will make a rough texture over the surface of polystyrene. PRACTICE on scrap polystyrene, or an old junk model FIRST. Do this until you're satisfied with the results. I hope that this will help.

~ Cobra Chris

You can make your finish rougher by increasing pressure a bit and holding the airbrush further away from the surface.  This works best with flat paint.  But don't make it too rough unless you are doing a large scale model.

Haptesthai

Hello, as far as I know, WWII tank paints often had uneven, rough, orange peel like texture. How can I achieve that?

 

correct me if I am wrong.

 

I think you are confusing that with the texture of the armor itself. Rolled steel plate armor is quite smooth. But cast armor can have quite a bit of variety in texture varying from orange peel to almost like stucco.

compare the texture of the transmission cover and turret, which are cast armor, to the glacis and side plates which are rolled armor. (click on the phoot for full size resolution to see the most detail)

You can use Mr Surfacer 500,you brush it on,and as it dries you dapple it with a brush imparting a rough uneven surface,you can adjust it to your liking.I use it on mufflers,but many experts use the technique on the entire tank,FSM even had an article in the magazine a few years ago.

It's not really a painting technique per se. Some kit manufacturers do make them with outstanding realistic looks such as welded turrents, zimmerts, rough surfacing and more. Dragon, Meng, Tamiya, to name a couple. It all depends on the tank you're doing. There are AM parts you can get too depending on what part you want.

You'll get better results by asking in the Armor forums here.