Ok here is the deal. You measure and add your nutrients in ml. It's just easier than tablespoons. You can get a huge 70ml
Syringe from the drug store for about $1.
Once it is in solution however, you need an EC or ppm meter to measure the concentration of the solution. Yes, using the EC readings would be easier but people still generally use ppm readings. You need the meter because some nutrients are stronger than others,plus you can monitor how the solution changes over time.
So eventually when people say "you want around 300-400ppm" for seedlings, you can add a little nutrients at a time to get to that level.
We are debating about how you reach or convert EC readings to ppm.