Its simple
fist off follow all sterile precedures as normal( sterile syringe, spray work room heavily with oust, etc...)
1 make a pot off boiling water( keep it boiling thru-out the proccess)
2 sterilize syringe ( i usualy wrap syringe in foil and PC it for 10 mins)
3 suck up boiling water into syringe and let cool to room temp
4 inject water into 100% colinized jar via one of the same holes you used to initially noc the jar up. using all the usual sterile precedures ofcourse ( alcohol wipe the needle and injection site, etc..) .it is alwase good to use your best jar for this, i.e fastest and strongest growth.
5 Repeat steps 2-4 untill desired amount of water is in colonized jar
6 shake jar ( this is where the mycelium cells are picked up in the water, the more you shake, the more cells)
7 Again, using sterile precedures and syringe, extract the now mycelium layden water into your syringe and use it to innoculate more jars.
you should notice growth within 3 days, and it grows FAST. The cake that was in the jar that was used to hold the water can still be dunked and rolled without any harm done to the cake.
I bet myc water is a good way to start an outdoor patch too
If you want to research it more just check out the shroomery. I learned this from reading one of roger rabbits post there, and that guy knows his shit.