Keep the car the whole time, unless you're starting out your holiday in Edinburgh or Glasgow. If you're starting out in either of those cities, you won't need a car until you leave.
You shouldn't have any trouble finding a place to park anywhere in Scotland outwith those two cities. It can be difficult to find parking in Aberdeen on a Saturday night, and parking in central Dundee is expensive (!), but other than that, just be sure to carry a decent supply of 50p, one pound, and two pound coins for the meters. Most of the metered parking involves putting the required amount of coins in to a centrally located meter, printing out a timed ticket, and placing it on the inside of your windscreen on the driver's side.
Almost every hotel/B&B/hostel in Scotland has its own dedicated car park. There are some hotels in the center of larger towns (i.e.: Inverness) where you may have to pay to park, but that's the exception, not the rule. I recently returned from a 30 day holiday in Scotland, and I don't think that I spent more than eight to 10 pounds on parking during that time.
Many smaller towns have a centrally located car park where you have to pay a small amount, but there's usually a sign directing you to a free car park. Don't ever park where a double yellow line has been painted next to the kerb, and if you're street parking, check the street signs for day and time restrictions.
You can also park for free, for a limited amount of time, at many of the supermarkets (Tesco, Asda, Sainsbury's, Morrisons, Co-op, etc.). However, be sure not to stay beyond the posted time limit (usually 90 minutes or two hours). There are draconian fines for doing so. There used to be car park guards at many of the supermarket car parks. However, many of them have been replaced by CCTV.
As they used to say in the old Esso commercials, "Happy motoring!"