Hi Sharon. I waked into Rome on 20 September after leaving Great Saint Bernard Pass on 8 August. I had two nights in Lucca (could have done with a couple more it is such a lovely town) on 2 September. The path certainly got busier throughout Tuscany, but 'busy' on the Via Francigena means you may see 0-5 other walkers each day. I always booked my accommodation at ostellos etc 1-2 days in advance - more out of politeness than necessity. On the via Francigena many of the ostellos are not staffed or are staffed by volunteers so it is best to let them know you are coming.
I also booked my accom in Lucca and Siena via booking.com as I upgraded when having a rest day and wanted to get something very central, so was a bit choosy.
I blogged everyday at
www.lifeonebigadventure.com - have a look at Day 24 onwards (from Lucca). Actually the stage out of Lucca to Altopascio was the most ordinary (lots of industrial estates etc) and I know many people who simply skipped this day - even though it is a short one - and caught the train.
Happy to answer any other questions if I can be of assistance. Bye, Mel