@Russell120: Be careful with long term renters longer than 8 weeks (especially if their mail is forwarded) as they are no longer considered "guests" but tenants. Tenant rights come into play after 56 days (in the US).
In regard to your questions:
1. If you are setup for "Instant book" turn it off. ***Don't use Instant book in general. You will have more problems then you would like.*** Open the calendar with the dates they are looking to book and ethier change the day prices individually or make a lump sum special offer. If you open the dates with Instant book turned off no one can book any dates without your approval so you can just decline any inquiry that tries to jump in there.
2. Change all dates to whatever prices you want. More $$ on the weekends, more on holidays, less on the weekdays. Whatever. I then log-out of my Airbnb account and go onto my Airbnb page and book the dates like I was a regular guest. I see what the total pricing is with tax and services and adjust my "special offer" accordingly.
Also...never use Smart Pricing. Its not very smart.