I would use a wood brightener (Jomax or the like) with a garden sprayer & scrub brush (if needed). Spraying can work fine as long as it is a decent spray and you put enough coats. As far as product, Sikkens is a quality product, others escape me at the moment. I personally would not use anything Behr or a store brand.

If you're going to spray the stain, here are three things to keep in mind:

1) Have a second person working next to you with a brush, this will help with penetration of the stain as well as ensure better uniform application.

2) Frequently shake or stir the container that contains the stain you are spraying as otherwise the solids in some stains will often start to settle out and you will get non-uniform coverage.

3) Use a big enough spray tip to prevent frequent clogging. Depending on the stain and the proportion of solids, sometimes a simple pressurized, backpack garden sprayer will work just as well as a spray rig.

Careful where the over-spray goes...