Newbie Image Editor: Help me produce cartoon branches?

[tomhart9]

Hi guys, I'm fairly new to the image editing scene and am looking for some tips on how I can create cartoon branches with similar quality to the trunk of the one below:

Although I don't use PS I use Paint.NET which is kinda a free PS copy with lots of the same features just in the form of plugins from the community, so any help, PS form or other wise would be welcome