I've had the Gardiners ones and they are ok, but I'd definitely buy the cheaper ones now.
I don't do many fsg on houses now, but if I do, I just put some chems in a bucket and dunk the brush in.
If I do a bungalow, I just put some chems in a 2 litre hand sprayer, hold my hand up high and walk along.
Again, conny roofs, a good hand sprayer should reach most of it.