Lots of thoughts on how to do this. I too like the simple turkey baster approach. I do it at every oil change.
However, the regular turkey baster you buy at the grocery store won't live long. They were not designed to work with chemicals. I've been through I don't know how many.
If this is the approach you want to take, go to Auto Zone or other mass-marketer auto parts store and buy a battery acid filler.
Here's a photo of one. You may have to click on the "expand photo" section.
I bought one of these a good while back and it's holding up much better than a turkey baster.
http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr=15616585&prmenbr=5806&usrcommgrpid=