L driver: I was in a similar situation to you last year, wondering whether to apply and how to prepare. Our 'local' grammar is about an hour an way on the bus and is hugely competitive so we were not sure about applying. I spoke to DD's primary school and asked for advice. Her teacher seemed to have no experience at all of 11+, and couldn't even tell us whether any of their pupils had ever applied, let alone successfully so it was very hard to gauge whether or not DD was in with a chance in a notoriously tough competition.
We did decide to go for it and to do it without a tutor. The Chuckra website was really useful for free video tutorials, free online tests and also some pay to use material. Chuckra also do mock 11+ tests which you can sit at a test centre or buy on line to do at home. This was one of the most helpful resources because they also publish the results and scores from the candidates, so you can get a reasonable idea of how your child is performing in comparison to the cohort. That's otherwise really hard to measure if you're doing it on your own.
The 11+ forum (the scary one!) was also very good for getting specific info on our school's exam and what material was relevant.
I think most kids for our chosen High School do go to tutors but we did the preparation togther without a tutor and DD got a place. All the resources you need are in the public domain and a lot of it is also free, so you can certainly do it yourself if you have a bit of time. There's no great mystery about the preparation; you just learn how to approach the various question types and then practice a bit so you can do them more quickly. You also need a good vocabulary and an eye for detail.