Glass Etching

[stand-in-line.livejournal.com]

So before I start on this little experiment, I'd like some info. I'm planning a pretty elaborate piece (no stencils involved, all free hand) but can glass etching be done without a stencil or masking it off? I've NEVER worked with the stuff so I'm unsure about the consistency, what it's like to apply, etc. Any helpful tips? Anything would be lovely, TIA :)