I am sure that many hydroponic guys use these plastic injectors, that you can buy from the farmacy. You can also inject various kind of fertilizer mix directly to your plants without making a mess and also you can suck any extra fertilizer out with the same thing without lifting the pots from the trays. Others use these large ones to inject christmas ham with salt, but my use is quite different. 
My tip is to buy couple of those 100ml plastic injectors for the kind of use, i ended up using them.
My tip is to buy couple of those 100ml plastic injectors for the kind of use, i ended up using them.