A free app for Android, by Udenity.

How to draw weapons. Skins is an app for a detailed drawing of your preferred weapon. You may learn the fundamentals of sketching with lessons of varying levels of difficulty. You’ll have no trouble planning what and how you’ll draw.

This application is for you if you want to learn how to draw awesome and realistic weaponry so that people will be envious of you. The application has a vast library of detailed sketching tutorials. It is a step-by-step instruction that is used to provide all lessons on drawing firearms. You may learn to draw quickly and at the same time you will have fun.