yea, its stressful on your fish otherwise. be patient and do it without fish, if you do a fish in cycle, chances are you'll be wasting money on fish...
Snails would go in after the fishless cycle is complete. Don't waste your money on test strips, they are horribly inaccurate and expensive. Get a liquid based test kit instead as they are the most accurate that a consumer can buy plus you get way more tests for the money.
Most of us in the beginner section like and use the API Freshwater Master Test Kit. It ends up being a bit of a common "lingo" for us when we discuss things sometimes. The Nutrafin Mini-Master Test Kit is also pretty commonly used and spoken well of. Tetra also make good liquid tests and there is a company called Salifert that makes even more accurate tests than most of these.
It doesn't matter when you put snails in after cycling. They could go in before, simultaneously or after the fish go in.
When you do a fishless cycle you have no living animals in it at all, your ammonia source can come from either adding a food product such as some fish flakes or raw shrimp (found in the grocery or fish market) or by adding household ammonia (be sure to get one that has no surfactants).
By adding the food product you are waiting for it to decompose, one of the by-products being ammonia which will begin feeding and cultivating the bacteria already present in miniscule amounts in your tap water. This method has the disadvantage of not being able to accurately measure the amount of ammonia produced.
Or, as I said above, you can add household ammonia, this is the preferred method in that you can accurately measure what goes into your tank. You can speed up your cycle by adding some pieces of a mature filter media to your filter. Because the mature media already have thriving bacteria colonies it won't take as long for them to increase in numbers.
As drobbyb & waterdrop said, liquid test kits are more accurate and are cheaper per unit used than test strips.
I highly recommed reading the articles in the following link if you have not already done so:
TBH it's been several years since I've done a fishless cycle, but I believe the only time you need to do a water change during the cycle is if your PH crashes, and the only purpose of the water change is to raise the PH. Adding baking soda during the cycle can help avoid that I believe. I'd wait to see what others say first since, as I said, it's been awhile since I've done one.
There is no need to do water changes during a fishless cycle. You dose ammonia as needed to develop the bacterial colonies and when you are getting ready to add fish you do an enormous water change to get rid of the nitrate that has built up over the weeks. If you get in trouble with a pH crash, you do a bi water change to bring the pH back up by removing some of the nitrates and replenishing the buffers in the water by adding tap water.