I've stained wood (USA) for decades and never used a pre-stain conditioner. This is the first I've heard of it. One article says: "A wood conditioner is basica

I've stained wood (USA) for decades and never used a pre-stain conditioner. This is the first I've heard of it. One article says: "A wood conditioner is basically a wood finish reduced to a very thin consistency." Sounds like a money-making product to use on very porous wood that has water-damage (rotted?) or has been repeatedly treated with solvents, leaving only weak wood fibers. I usually replace such wood. There are also products for "rejuvenating" rotted wood: https://duckduckgo.com/?q=rejuvenate+rotted+wood&t=opera&ia=web https://duckduckgo.com/?q=rejuvenate+rotted+wood&t=opera&ia=... I suppose these have their place but I have been lucky enough to not need them.