There are lots of options for pool exits for dogs. I've never used it but the Pet Classics dock looks really well made. http://www.petclassics.com/Water-Ramps-Steps/dog-on-water-ramp.29.html?image=538

I would also suggest you keep a dinghie in the pool at all times so that your dogs, and any creature that might fall in, have something to swim to when they're tired. http://www.doggiedinghies.com/e107_plugins/autogallery/autogallery.php

Be sure to take time in training your dog to use the exit platform so that it's always a positive experience for him (them). Last thing you want is one of them trying to climb out between the ramp and pool wall! : )

Here is a link that might be useful: Here are even more options

Yes, you can get drop-in steps for a vinyl-liner pool. Lots of models from a variety of manufacturers. We got the steps initially for us---it's much easier to enter and exit the pool via steps, and the handrails give extra security.

We've taught all of out dogs (as well as all of our friends' dogs) on how to use the steps. No biggie---you just need to train them to NOT flail wildly along the edge of the pool but go directly to the steps to exit. I find that tiny bits of salami work really well :o)

I think the solid plastic steps are a better option that the floating ramps, since they work for pets (especially large dogs) as well as small children, the elderly, limited-mobility swimmers, and the rest of us.

We take the steps out in the winter (we are in New England), and put on a very sturdy cover that connects to metal in-ground posts. I've stumbled onto this cover and got wet to the knees, but bounced right back up again. The dogs race back and forth across it throughout the off season (typically there will be a foot or less of water on top of the cover when they stand on it). Eventually it all freezes for the duration of the winter.

We've replaced this style of cover twice in 22 years. It did not need to be replaced because of any wear caused by the dogs, rather the stitching eventually gives way probably due to the long-term effects of UV etc.

Hope this helps.