I use an eyedropper to dose the tanks when I turn the lights on in the morning. It can accumulate over time so I'll skip the dosage every 4th day. Ideally you can dose 1-2 hours before you turn on the lights to give it time to fully disperse but I have a long enough photo period that it doesn't matter.
I don't use recommended amounts either - I dose 1 drop per gallon for the small tanks and 1 drop per two gallons for the larger 20+ gallon tanks. The bottle lasts much longer that way and I didn't notice any difference when dosing more.