I'm sure that applying a printed film to any surface is perfectly viable. However, the starting prices from that place seem a little high.
I have also been experimenting with Camo finishes lately. I wanted to mod a PC case and give it a military look for use with a simulator. I must say that it turned out reasonably well. As this was to be used in a WW2 simulator, I was going for the WW2, blocky,hard edge, camo look similar to the armored vehicle below. It took about 15 minutes for prep and about 20 minutes for the base coat to dry so I could mask it.
Here is the finished product:
I have been favorably impressed by some of the new Krylon Camo paints. For Plastics or metal, the new Fusion paints work very well; the pigments are fine enough to cover easily and the spray pattern from the new nozzles is excellent allowing you to get thin even coverage. The paint is dead flat and dries to the touch really quickly. The nozzles don't clog like most spray bombs. Paint goes on smooth and is self-levelling. It is really easy to get a professional look.
Plastic adhesion is excellent. Their new
Camo line has excellent durability as well. As with any paint job, prep is important and the surface to be painted should be clean and free of grease and oils. I haven't done any firearms but have used the Krylon Camo system on a few items (both metal and plastic) and I have been very impressed with the durability, ease of application and the end result. The best part is that most cans of Krylon are about 4 or 5 bucks (US $) each. Even better is that if you don't like it, you can always strip the paint off and do it over. After the finished paint job has dried properly, it can be sprayed with a flat clear coating to protect the paint.
The main issue is that I have no idea what the availability of Krylon paints is (in India).
Krylon
Camo Line fact sheet
Here is a Suzuki sidekick with a camo paint job using this setup:
http://www.krylon.com/projects/sports-r ... -sidekick/
Some techniques (from Krylon):
stencilling-Leaf camo (using appropriate colors)
Camo Stencils. You can make your own, e.g. if you want to do digital camo, etc.
Camo Painting Tips
How to paint Camo patterns
Some examples:
Camouflaging Rifles
How To: Paint Camouflage, Template and Freehand
Painting 101
Full Camo paint job