Any good advice for a realistic netting and foliage on tank barrels ?

On a model, I presume.

Use Revell’s Contacta or very dilluted white glue (wood glue).
If you sump the netting in a mix of white glue and water it can easily be drapped around the barrel. Leave it to dry for half a day. The end result will show a natural form, as on the real thing where, due to the weight, there will hang quite some of the netting under the barrel.

If this is for modern tanks, I tend to cover most of the vehicle - which is a bit of an act of faith in obscuring detail - not just the gun barrel. Bear in mind that most modern vehicles are often nearly completely obscured with camouflage netting and scrim so it's a fine balance in replicating the real thing yet still enabling the viewer to recognise the model.

I use medical gauze which I soak in diluted white (PVA) glue; I cut the gauze roughly into 2inch squares - it doesn't matter if they overlap on the model. I would recommend using something shallow like a saucer for the glue as the gauze will immediately soak up the liquid (which of course is what it's designed to do) and it then becomes a bit of a nightmare to handle. However, using tweezers, I then drag it out and re-form it into a rough square or rectangle and then drape on to the model. You might wish to dip it onto a paper towel first to remove the excess glue.

Once it's on the model I might move it around a bit using the tweezers.

Once dry - and again I stress this is to replicate modern camouflage systems - I add more PVA glue (although really any glue will do) and add layers of used tea leaves; this must be fresh tea as the contents of tea bags are too fine and are really a sort of dust.

Add sufficiently for your purposes ie to depict what you are trying to replicate then let it all harden off.

With a coat of primer on it starts to make the model AFV look quite warlike and purposeful. Paint according to your references; for instance, British Army camouflage nets from roughly the late 60s were composed (in addition to the net itself) of a plastic like triangle panel, green one side and brown the other, attached to the net with small clips. Of course, once draped on a vehicle there was often not that much net to be seen, depending on how close together the patches were affixed.

For WW2 vehicles and say, up until the 60s, netting had Hessian strips tied or woven into it. This is a bit harder to reproduce although I have tried using strips of Tamiya masking tape. Use the gauze method as described above then try and integrate the strips of masking tape. The real thing was composed (in British service anyway) of rolls of Hessian coloured green and brown, roughly 2-3 inches wide. These were cut to the desired length and then attached to the net. Before the plastic panels came into service the Hessian rolls (in British use) were replaced with a plastic roll, coloured green one side and brown the other.

Of course, natural foliage could be attached to both types of net and on my models I tend to use etched brass leaves from those manufacturers such as Eduard. As long as the branches are glued together and twisted a bit to help create the illusion of 3D, this can work quite well, in my opinion.

I've banged on a bit here in explaining all this; I hasten to add I really discovered how to do this from an old Verlinden book although can't quite remember where the tea leaf idea came from (as opposed to the model railway flock advocated by Verlinden).

Anyway, I hope this helps; if you send me a PM I'll try and forward some pictures of my models thus camouflaged.

Brian

Cheese Cloth makes an excellent scale netting. It needs to be soaked in an earthy colour. Tea works. Try Liquitext Matte Medium or equivalent for an adhesive. It is essentially a flatter version of PVA glue

For looking accurate you could do

http://www.plasticwarfare.se/2007/10/how-to-make-realistic-barracuda-camouflage-netting-in-135/

or buy

http://www.detailscaleview.com/2015/06/voyager-model-135-modern-nato.html

http://www.voyagermodel.com/search.asp

http://www.amiami.com/top/detail/review?scode=TOY-SCL2-47953&page=