If you must spray, turn the nozzle setting to the finest setting...like a mist fog.

Yep - when I spray bt on my brassicas, I use a crappy little sprayer from the dollar store. The mist is super fine, It takes longer, but there is a lot less waste too, and that stuff is pricey.

You could try a spreader/sticker.

Generally, I find that dust works much better than sprays. Even a superfine mist doen't guarantee that the chemical will "stick" in a uniform manner.

Dusting works well though.

Desert weed have a waxy coating that tends to cause beading of sprays. The best method I have found for spraying desert weeds it to add so much dish-washing detergent to the liquid that the results is foaming them. This might work for other sprays too. Might require too much washing of harvested broccoli.

When I used to grow a lot of broccoli, I would spray BT
with a pump sprayer. Due to the smooth hairless leaves, I would add a sticking agent to the spray (a few drops of dormant oil).

Later when I grew a dozen or less plants, I just mixed the BT in a quart mister bottle. This produced such a fine mist that I no longer need to add a sticking agent. Do not
over spray to the point that the spray runs off however. Just a nice mist is sufficient.