1

If you hire a car to go (for example) from Jaipur => Pushkar, then you will also pay for the driver to return to Jaipur, so you pay a double rate.

This may end up being more expensive for you, rather than hiring a vehicle to take you around for the 6 days.

Depending on the size of the car, the rate will start at around Rs.8 per km. You will also pay for a room for the driver and, it would be nice if you have him join you for breakfast /dinner meals - some drivers will choose to sit away from you, but that's your call.

At the end of the journey, it's also commonplace to offer a gratuity to the driver of around Rs.200 per day. I'd pay this only if the driver does a good job and you don't feel threatened.

Not sure about Ranthambore...

2

What are your starting point and end point? When are you travelling? As Zoltan suggested it is better to hire a car for the tour starting from say Jaipur & ending at Jaipur.

3

The Ranthambore park would be closed till Oct. For Pushkar, you could take atrain/bus to Ajmer adn take a taxi for the drop to Pushkar ( 13km away).

4

For time efficiency, night trains are helpful for hops greater than 7 hours or so. You get to change locations without using up much, if any, daylight time. Of course they are a good idea only if you sleep reasonably well on trains.