What I actually do:
I have a 55 gallon drum in the basement. Top has been cut off so it is open on top. Using hoses, including a "T" that allows me to run hot and cold water into the drum, I can fill the drum with water. The hoses are simple hoses of type used to connect laundry wash machines to the water supply for the basement wash tubs. This feature is not usually found in apartments. You got to have an old home with a basement. There is a concrete floor with a floor drain to the sewer if there is an overflow. The floor drain is only a few inches away from the 55 gallon drum. The occasional "overflow" is inevitable, no matter how diligent you are. I absconded from work a 3/4 horsepower centrifugal pump. This would have been prohibitively expensive if I had to purchase the pump. The model I have is much larger than needed. You could get away with a much smaller lower pressure pump. The intake hose is short, from the inside bottom of the 55 gallon drum, to the inlet to the pump. The outlet is 50 foot garden hose with a brass shut off at the end. When not in use, and preparing for use, the 50 foot of outlet garden hose is coiled up in the basement, while still connected to the pump.
Fill barrel with water. Hang outlet of garden hose into drum, prime pump if needed (whether you need to prime the pump depends on centrifugal, centripetal or impeller driven pump) This begins to recirculate the water in the drum. The pump should be powerful enough you can see ripples on the surface of the water. Add sufficient fertilizer to dose the water to your desired ppm as Nitrogen, or if you prefer use Total Dissolved Solids as your key parameter. I like to dose based on nitrogen levels, 40 ppm in cool weather 120 ppm in May-June peak growing weather. You need to make the calculations yourself from the brand of fertilizer you are using, because those numbers on the bottle do matter. A 30-10-10 will be dosed quite differently than a 12-1-4 . I use a 12-1-4 most of the time and my dose ranges from 1/4 teaspoon/ gallon to 1 teaspoon per gallon. There are times you might want to go heavier or lighter depending on your frequency of fertilization and the main species you are targeting. Typically I do low concentrations, 1/4 teaspoon per gallon, more frequently, weekly or even more frequent, versus higher concentrations, less frequent.
When thoroughly mix, using the brass shut off at the end of the hose, I stop the flow, attach the watering wand with a Dramm water breaker rose (nice 1000 hole rose, gives a soft spray) I drag the hose up the stairs. Drag, because it is full of water, and somewhat heavy, then I begin watering my bonsai, which are all within about 30 feet of the back door of my house. I can simply add another length of hose to water further away.
This is where a centrifugal pump is superior to a less expensive diaphragm pump. You can use a valve to start, stop or throttle back the flow of a centrifugal pump without damage to the pump. The centrifugal pump works with vanes on a spinning disc moving the water in a chamber. If flow is restricted or blocked the disc with its vanes still has enough clearance with the pump head housing to keep spinning even though the water can't move.
A diaphragm pump if throttled back or flow stopped without turning off the pump will burn out rapidly. The diaphragm pump has a flexible flap that more or less completely seals against the pump head housing, as the shaft turns the flap moves a quantity of water from the inlet to the outlet. If there is back pressure, there is no room for the flap or diaphragm to keep moving, the shaft of the motor must stop, causing the motor rotor coils to overheat. Diaphragm pumps can not tolerate back pressure..
There are other types of pumps, you need to investigate before purchasing. Key to check is how the pumps tolerate back pressure if you were to restrict flow while watering your trees. Centrifugal pumps are great in this aspect, but they tend to be quite expensive. Swimming pool filter pumps tend to be centrifugal pumps, you might be able to find a used pool pump on Craig's list.
They beauty of my system is my dilution is to the final dose rate. Right there in the 55 gallon barrel. If you have the room to set up a similar system.