Here's a piece of construction grade pine that I stained in Rustoleum's Kona color after applying a wood conditioner. I probably could have sanded the wood better to get an even finish, but I think the Kona stain looks beautiful. I'm thinking about applying a second coat of stain.

I was wondering whether, when using wood stain with a wood conditioner, do you apply wood conditioner in between each coat of stain.

I learned from others that you don't. You only apply wood conditioner before the very first coat of stain and you don't use wood conditioner after the first coat of stain.

My sources on this are:

Using pre-stain conditioner with multiple coats of stain (post #154891) which says, "No, you only use the conditioner before the first application of stain." and  "If you use the conditioner after staining, it will lift the stain you already have down."

and

Wood conditioner between stain layers which adds that wood conditioner should be applied "...only before the first. Wood conditioner's job is to manage stain absorption in woods which would otherwise soak it up strangely. Once that partial pore-filling has been done, stain shouldn't disturb it."

So only apply wood conditioner before the first coat.