Text format input filter problem - cannot get style attributes to work

I'm using CKEditor on a client's site and cannot find any documentation that shows how to create a text filter that will let a user enter style attributes (like changing the size of text). And by "user" I mean someone other than a trusted admin, so "Full HTML" is not an option.

Note - I'm not having any issues setting up CKEditor itself (either standalone, or with the WYSIWYG module), just the input filters...

I am clearly not the first person to want to do this so I'm assuming there has to be instructions out there somewhere. While I have found a bunch of information on what needs to be done - disable the "limit allowed html tags" option, install some other filtering system (like htmlpurifier), then set up filtering to allow for the limited tags & attributes I want available - I can't find documentation that tells me exactly how to do so, and nothing I've tried so far is anything close to self-explanatory.

My best guess is that I simply don't understand this issue well enough to enter the correct search strings into google to get me the answers I need. Any / all help will be much appreciated.

As usual, links to helpful info would be more than sufficient. Thanks!