Hi,
1. The most important are wild grass JLF and crop residue JLF. Those can be used on crops at any time during season from the seedling stage to harvest.
On cucumbers use crop residue JLF made from rotten cucumber fruits, cucumber leaves and stems.
Sometimes it is necessary to speed up plant's growth. Then, JLFs that are rich in nitrogen are used in combination with wild grass JLF and crop residue JLF.
Fish JLF, fish guts JLF, fish meal JLF, fresh blood JLF, blood meal JLF, kitchen waste JLF and urine JLF are all examples of fertilizers that contain a lot of nitrogen.
Situations when other JLFs are required are rare.
2. Any size from 1L to 20,000L is good.
3. Potency of JLFs vary greatly, it is your job to figure out how much to use.
As a start, for every square meter, weekly, use 30ml of JLF diluted in more than 3L of water.
Use more or add high nitrogen JLF if growth is slow.
In case of excessive growth, reduce the amount or stop feeding.
Always add JMS when feeding JLF