I personally prefer using a brush as well. Also lets me get the edges of the plywood which is more important.Brushing is really best for any exterior wood application. It allows you to work the stain/oil into the cracks in the wood and fill them up. Cracks is also where water can sit and rot will be the first to start.
It was 95 today; and we haven't had measurable rain in a month; dang grass is so crunchy it sounds like walking on rice crispies.I use motor oil or used hydraulic fluid whatever I have an abundance of at the time but I try to cut it with an equal amount of diesel fuel. I try to apply it on a good hot day ( which where you and I are there is no shortage ) I use a paint roller on a stick with a roller screen in a 5 gallon bucket and it soaks in just fine, a mop will work to and a lot faster but IMO you waste an awful lot and definitely not as environmentally friendly.
Facts.It was 95 today; and we haven't had measurable rain in a month; dang grass is so crunchy it sounds like walking on rice crispies.
UV protection comes from a darker stain so used motor oil would have more UV protection than linseed oil.Neither BLO or waste oil has UV protection so you'll still have some issues down the road