I am new to ExtJs 4 and I am in the process of customizing one of the default themes. The CSS is massive and there are loads of icons that come with each theme.

My custom theme required is very specific and will require me to replace most of the icons. What are the tricks/tools available to me if I dont have much time? Are there any out of the box tools I can use apart from from relying on Firebug editor?

I understand that Compass and CSS allow for customizing colour changes, is there anything else?

Also where can I find the best information on ExtJs 4 theming?

Thanks for your help.