
Twisted Brush 3.5 for Windows has a lot of the features of Corel Painter—brushes that blend, paper texures, artist brushes—for free.

Pixarra’s Twisted Brush is a full-featured digital painting program. Pixarra has released version 3.5 as freeware; they hope that once you try the freeware version you will want to try and buy the newest version, Twisted Brush 9.0.
TwistedBrush Free has natural art brushes that look like watercolors, oils, pastels…oils look thick, airbrushes soften the edges of the “sprayâ€. Blending brushes let you blend and smudge either wet or dry, and you can choose the texture of the paper, including hotpress and coldpress watercolor and several weights of canvas, and even silk.
The tracing paper feature lets you use a photo as a guide for a painting, and Twisted Brush also has cloners and masks. Art Sets of brushes and the ability to record a script are other features that will surprise you in a free program.
Twisted Brush Free is truly free, fully functional software with no nag screens and no limits. After trying the few version, if you decide you want to purchase Twisted Brush 9, you have several options: you can purchase as little as a 6 month license for $39.95, a one year license for $59.9 or a perpetual license with free updates forever that never expires for $129.95.
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Download Twisted Brush 3.5 Freeware
Download Twisted Brush 9 Shareware

I have tried it, and a very impressed with this program. it will be a while before I could purchase the larger version, due to winter utilitiy oncerns, however I fully intend to do so