optimized resources needs to be pre-generated for custom skin, the issue is covered here:
Currently you need to setup Maven build to do packaging , or use build-in skin:
there is no built-in solution for non-maven based projects,
but what would you need to do is building command-line interface for richfaces-resources-maven-plugin.
The base class which is responsible for generation is ProcessMojo ,
it can be simply replaced with class with main(args) method.
We have already taken same approach for cmdline-generator  as alternative to richfaces-cdk-plugin 
and it works like a charm!
it will look pretty similar like ProcessMojo,
but you will need to provide all necessary attributes from command-line.
ProcessMojo has many fields which are injected by Maven.
If you will look on CommandLineGenerator, it is similar to GenerateMojo, but instead of Maven, it uses dependency injection of command-line parameters, which needs to be processed then to expected form.
Finally, it will be used similarly to GenerateMain:
To start up quickly, you can fork the CDK repository with cmdline-generator feature , and duplicate and modify cmdln-generator maven module.
One thing i don't understand is that in the official documentation, it says this:
there would be no problem with the resources, but it is not working that way; i have that entry in my web.xml file, but i still get the errors
JSF1064: Unable to find or serve resource, org.richfaces.staticResource/4.2.2.Final/Packed/myskin/skinning.css.
JSF1064: Unable to find or serve resource, org.richfaces.staticResource/4.2.2.Final/Packed/myskin/packed/packed.css.