Pooh,

You can use nylon stockings. The holes are small enough not to let bits of nutes escape. Just steep them in some hot water for a while if you have a TDS meter then just test to see how well they are dissolving. If not then just leave them in there for an hour or so. You should notice that the water is cloudy at that point then just water as needed with your blood meal tea. Keep an eye on the PH though blood meal is very low PH. Be sure to allow your tea to cool before watering also. Also remember that you will need to supplement your blood meal with all the other macro and micro nutrients.

Herbus
Herbus