Painting gestures is sometimes also known as gesture drawing. The two are similar subject areas in art but they are not exactly the same thing.
Painting gestures in humans and animals has a lot to do with how you intend to depict motion in your artwork. If it is a very realistic painting then you are in for a real labor of love. Many people use photographs and wooden artist’s models to get the posture just right. Then they faithfully replicate it on the paper as they see it.
Realistically capturing human poses is also known as mechanical drawing. The more faithful a drawing is to real life, the more mechanical it is. However even mechanical drawings are sometimes sketched quite fast. Many mechanical drawings are also used as the basis for the paintings that feature depictions of active humans and animals.
However true gestural drawing is also known action drawing for obvious reasons. It is all about capturing motion. This can be quite a difficult discipline to learn, especially in realism, because it is not really about representing something truly but rather drawing body movements. Your intention is to not really paint what something looks like but what something is doing.
A popular exercise for practicing painting gesture in humans is to get a model. The model should change poses every sixty seconds while you attempt to quickly capture what the model is doing on a sketch pad. You don’t have to use models for this. You can use pets or family members. You can also just sit in a public airport and sketch away.
Gesture drawing is based on the principle that movement is intangible. When you do gesture drawings you are trying to go beyond mere appearances and capture the very essence of your subject. Working very quickly is also very essential to doing this properly.
Some people do gestural drawing of inanimate objects to give them character and personality. In fact some of the best artists in the world are able to give human qualities to things that are not human at all using the principles of gesture drawing.
Most drawing masters suggest drawing what you love, whether it is nudes, cars, cats, flowers or monsters. This is the best way to master the complications of creating realistic gestural or mechanical drawings.