If you think your paintings are too tight and controlled, this collection of tips and techniques to try should help you work in a looser style. Don't dismiss a technique without giving it a good try as while it may seem unlikely or perhaps even daft, you may well be very surprised by the results. There is, of course, no 'magical' way to suddenly loosen up the way you work. Like everything else in painting it's a goal you have to pursue. But one that is achievable through practice and persistence.
Tip 1. Use the 'wrong' hand:
If you're left-handed, put your brush in your right hand, and if you're right-handed, put it in your left. It'll feel awkward and you won't be able to paint as precisely as you can with your dominant hand. This lack of co-ordination also means that you can't get into that automatic paint mode where your brain says "I know what an apple [for example] looks like" and you paint an idealistic apple rather than the one in front of you.
Tip 2. Work in the dark:
Well, not complete darkness, but in reduced light where you can't see every last bit of detail. Try lighting a still-life with a strong lamp from one side (oblique light). Or if you can't change the light, squint your eyes so the lights and darks in your subject become stronger.
Tip 3. Leave stuff out:
Our brains are quite adept at filling in missing details, so you needn't put down every single thing. Take a long hard look at your subject, trying to decide which are the essential bits. Put down these only, and then decide whether you want more detail or not. You'll be surprised at how little can be necessary to capture the essence of something.
Tip 4. Don't paint outlines:
Objects are three-dimensional, they don't have outlines. If you're unsure about this, look at your body and see if you've got an outline or if you're 3-D. You do have an 'edge' when you look at e.g. your leg, but as you move, so this changes. Instead of drawing an outline (or painting one) and then filling it in, paint the object as a whole.
Tip 5. Let the paint drip:
Load your brush with lots of dripping color and let it run down the surface of your painting as you apply it to the 'right' place. Don't tidy up the drips. They add a fluidity.
Tip 6. Try unrealistic colors:
Instead of worrying whether you've got accurate colors, try some that are completely unrealistic. Paint a self-portrait in your favorite colors rather than skin tones. The result will probably be a lot more emotive – and certainly dramatic.
Tip 7. Paint with water:
First paint your subject with clean water only (okay, not if you're using oils!). This familiarizes you with your subject. Then introduce color, which will flow into the wet areas. Don't try to stop the paint from spreading or worry about the colors becoming 'wrong'. Wait until you've finished, then see if you like the result.
Tip 8. Apply masking fluid:
Masking fluid enables you to block out areas a watercolor so you don't have to worry about accidentally painting there. For example, instead of painstakingly trying to paint around the petals of a white daisy, paint the petals in masking fluid first. You can then paint freely safe in the knowledge that your white petals will appear pristine when you rub off the masking fluid (do it as soon as your painting is dry; it becomes harder to remove the longer it's on the paper).
Tip 9. Use a BIG brush:
Painting with a big brush makes it hard to put down detail. A big brush encourages you to use your whole arm to make broad, sweeping strokes. Use a flat brush not a round one because you're wanting to increase significantly the width of the painting strokes you make.
Tip 10. Use a ridiculously long brush:
Take a stick at least a meter/yard long and tape it to the handle of your brush. Put a large piece of paper on the floor. Now paint. The long brush handle exaggerates the movement of your hand and arm, creating longer marks on the paper than you'd usually make. Don't fight this by trying to make smaller movements!