Is there a better way of doing this? Is it better to build up, it's getting better, ie you are getting what you pay for? or other way around.
pls share your experiences (assuming they are located in around the same vicinity).

I always show the best first. That way they know what's possible and they reject the dogs more quickly.

ditto, unless there's some other reason to schedule a different order

I'm not sure that you can always decide the order. Many vendors/listings aren't available at the different times you need. Instead of going A, B, C, D, the odds probably are that you'll have to settle for C, A, B, D.
But the key, I think, is to have the "right order" in your own mind and to then show each listing with appropriate comments. For example: "I've had to show you this one first because this was the only time the vendor would/wouldn't be home. However, I suspect you'll agree that it isn't quite what you're looking for / not good enough. So let's just rate it on a scale of say one to five and then see how the other three we're going to see compare with it."

Duncan