-Remove the lid from your tank.
-Does your tank have a heater? can you increase it to about 80 degrees?
-Keep the filter running to move water around the tank.
-I want you to either get a tupperwear or Ziploc plastic container or whatever..... Something small like .5 or .25 gallon sized. (dollar stores here sell small kritter keeper type things for kids to put bugs in they work great their just under half a gallon each) If you can get 2 containers this will be even easier. This will allow him to get to the surface easier.
-Float this container in your current tank, use a clothes peg or elastics to attach it to the rim of the tank so it doesn't tip or float around.
-Get a 1gallon bucket and mark it with sharpie at the half gallon and 1/4 gallon (mark at each 1 quart)
-run your tap to 80 degrees (or whatever you tank is heated too) and fill bucket to half gallon or full gallon depending on how large this container youre using it.
-add appropriate amount of AQ salt (1/4tsp per quart... 1tsp/gallon) and stir to dissolve, add dechlorinator.
-if you have 2 small containers fill the one your fish is not in with this new water then gently move your fish to this new container. Rinse out his old one and prepare for his next water change. Otherwise you may need to hold him in a small cup for 2 mins while you do all this.
I personally like to use 2 small containers and as soon as my fish is transferred to the new water, I rinse his old one out and add new water, so the new water actually sits for a day before he goes into it, then I know its the exact perfect temp, so in a sense I get his new water ready a day in advance. And if you make up 1gallon of salted water at a time, and you need to medicate with something else you're not wasting as much if his small temp container is only 1/4gallon. You can keep it all the in bucket for a day or so

Plus then you don't have to worry about measuring appropriate amounts of salt or meds if both containers you have are totally different sizes.
It should all take less then 5 mins a day.