Best way to upload to Google Base?

I am close to launching my website but definitely want to use Google Base for marketing. Currently I have an eBay store and I use the Google Base Store connector to upload my store to Google Base. My question:
What is the best way for me to do it from an OS Commerce Based Store? I see that Google Base Store Connector in addition to eBay also has an option to upload from OS Commerce so am I correct that it would work from this? I see options from within the program also for uploading to Google Base. I know some of these may be more automated than using Google Base Store Connector. I also see how you can even download to a spreadsheet to then upload to Google Base. What I'm asking for is what is the most efficient way that does a good job to upload to Google Base?

What is the best way for me to do it from an OS Commerce Based Store?
If for OS Commerce - then you are on the wrong forum....

If for Zen Cart then get the Google base feeder that creates a XML file for this

http://www.zen-cart.com/index.php?main_page=product_contrib_info&products_id=473

I have a question... Because of MAP agreements I sometime don't show a price for the item in the description, You would have to add the item to cart to see your final price. In using the feeder how would it handle this?

I can't have it show the low price because of agreements.

Thank you,

Flux