Using Solr with MySQL

I was browsing some questions here concerning MySQL and faceted searches and I saw one response that suggested the use of Solr.

In my MySQL database, I have many tables for products, suppliers, messages, users, etc - all interconnected. How would I use Solr to do faceted searches for products? From what I understand, I'd have to keep feeding Solr product data from MySQL - but how do I deal with indexing the data? Do index right after adding a new product? Do I batch index? How do I deal with Solr accurately representing data that is found in my MySQL database? (inserts, deletes, etc)

Thanks in advance.