The main ingredient of any dechlor is sodium thiosulfate, and it will neutralize chlorine and in chloramine, will break the chlorine/ammonia bond, neurtralize the chlorine and free the ammonia.
Products like Prime and Amquel will also render the ammonia, released from chloramine, harmless...which is great if you don't have a cycled/established tank and filter. If your tank and filter is cycled, they should be able to take care of the very small quantity of ammonia that is released.
Prime and Amquel are probably the best products you can buy...but if you are doing lots of water changes or the amount of water in your water changes is very large...as in large tanks and ponds, then straight sodium thiosulfate is more economical. And as I said, as long as your filter is cycled, you should not have to worry about the small amounts of ammonia released from chloramines...the nitrifying bacteria will take care of it. You can buy bulk sodium thiosulfate very cheap...5 lbs will cost about $15-20 and will treat over 100,000 gallons.
Also to note, it's very, very, very hard to over dose using dechlor.