What are some good brushes for doodling and sketching in Photoshop?

[aqua03]

So I was thinking a bit about trying to get more into just quick doodles and drawing studies in digital art. However, I realized that my current art style and work flow pipeline seems to lend itself more towards "Completed" works so to speak. (Rough sketch, refined sketch, line art, colors, shading and details, etc.) as opposed to quick, rough, but still good looking and clean, sketches and studies. (See examples below.)

So what are some good brushes for quick colored doodles or sketches and studies plus what are some good tutorials to get started on that type of digital drawing?
Especially regarding animals and scenery? (Which is where I feel I need to brush up on the most recently.)

Thanks for the help.

[JeanGuillet]

Adobe Photoshop | Download exclusive brushes from Kyle T. Webster

This enormous brush set from Adobe itself I've found to have just about everything you could want. It's got a great comic inkers, pencils, a full manga-creation set, landscape brushes for concept art, and special effects brushes. Great place to start and there's thousands of brushes to choose from.

[aqua03]

Ah, yeah. I've downloaded a few of their brushes before. They're really good, should download a few more sometime. Thanks.

[Tanidreams]

I recommend Helen Chen's brushes, the texture is beautiful and she has some good sketch brushes too: http://www.mediafire.com/download/mo1...

Here's a video to a professional youtuber I follow, Lulu Sketches. She linked some really good brushes in the description:

[aqua03]

Neat, thanks! I'll have to check her out some time as well.