Welcome!
There are liquid pumps you can get that are automated. Someone can probably give advice, but it doesn't seem to be a very popular opinion.
Putting it by the return is just to help it mix in - you could put in a little at a time at the deck where it's easier to pour it slowly and gently and use a pool brush to mix it in when done.
I have always injected bleach/chlorine into my pool. (Except when the PB started the pool).
I learned this method right here and others in here use the same method.
A Stenner injection pump is used to accomplish this. Its a peristaltic pump that uses a tube and 3 rollers to "pump/displace" the chlorine.
I have their 15 gallon UV treated tank and connected it to the chlorinator installed by the PB.
These pumps are very reliable and precise and have been using mine for over three years injecting .9 ounces per minute.
For my pool to increase 1 ppm is about 30 to 40 minutes depending on bleach concentration.
Why do this?
I do it so that I can control my stabilizer (CYA) concentration separately from chlorine and I can literally dial in exactly how much chlorine I want to inject.
As a result my stabilizer concentration never goes higher than say 40 ppm and as a result I can keep my chlorine concentration below 5 % and always effective.
Refer to the Chlorine concentration/CYA chart somewhere in this forum.
Never have to dump my water to bring mt CYA concentration down.
Did it once and I hated to dump 12,000 gallons to bring CYA down to less than 50 ppm.
Puertex