For spindles the last few times we’ve used the carwash type mitts. They work pretty slick. Big rubber gloves, leather glove and then the mitt on last, on one hand. Trick is to just dip finger tips in stain because it slowly saturates the glove and gets messier as you go.
On floor we use brush between boards and pad on broom handle for surface. 2 coats in small sections and move on to next section.
I’m not sure why you guys are getting such short life out of your stains. We used some junk about 25yrs ago and the next time it was CWP? and SW since.
3 buildings are cedar, 1 deck 360sqft, dock, steps, another deck wraps around 3 sides of house, that one took 28 gallons, other deck is about 264 sqft. We use the SW on all them. Might have to look into blending some linseed oil.
Cleaning: we use bleach concetrate, spray on, then a Oxi clean concetrate, spray on, brush it in, re spary with bleach and then pressure wash off. Work in small 8′- 10′ sections. We buy cleaning supplies in cases to keep costs down.