In the early days of spraying Bt I used an old
Windex bottle to apply the fine bacterial mist.
That was a mistake I repeated way too many times before I wised up and
invested in the MintCraft
garden sprayer.
It's a well designed unit that holds a decent amount of pressure.
I give it about 5 or 10 good pumps which will last through a half
gallon of spraying. The extended wand allows you to easily target any
area of the plant while providing a convenient control knob for mist
level adjustments. It gets a bit heavy to carry if you fill it all the
way up, especially if you're using the shoulder strap. You might want
to upgrade the strap with some padding if you do the maximum capacity.