I use the liquid fertilizer at every watering (more in summer with high growth, less in winter with low growth). I mix it up in the watering 5 quart water can as if it were a 1 gallon watering can so it is always a little more diluted.
I water each plant from the watering can. being sure to give it a good drenching. I try to avoid the communal soak, but sometimes do it for my mounted orchids.