Are you using a pigment stain (like Minwax)?
There is no good way to do anything but block it.
Shellac works well.
Paint thinner will remove some of the stain. Alcohol not nearly as much.

brickeyee: thanks for your response.

Yes, I plan to use Minwax oil base: red mahogany.

When I mean I want to COVER UP PINE KNOTS, I want it to look less "knotty". (I'm sure we purchased the wrong type of wood/furniture, but there's no going back now.)

What do you mean by "block it"? Do you mean by hiding it w/ other pieces of furniture, or does shellac actually help the wood look more fluid/continuous and less knotty?

or should I just paint this cabinet/bookcase?
What color of paint would look most like the red mahogany stain?

thank you.

To stain pine evenly, a conditioner is necessary---pine has different grains and grain densities causing stain to often blotch. A simple conditioner is a one pound cut of shellac. That is done by mixing one pound of shellac flakes in one gallon of alcohol and letting the flakes totally dissolve. That mixture is then applied in one coat on the pine. The stain will still work, although less darkly.

There is no way to reduce the 'knotty' effect of pine---knots will even show through primer and paint unless several coats of each are applied and sanded.

Any stain is simply going to make the pine change colors---and look like stained pine. Which is not a bad thing as long as stained pine is the desired effect.

To effectively paint pine and cover the grain/knots to hide them, I apply three coats of primer---I use Zinsser BIN or Bullseye123---sanding between each coat. Then as many coats of paint as needed. There is one type of paint that covers pine grain/knots well---oil based alkyd enamel---two coats over just one or two coats of primer will hide the grain/knots. But that stuff is expensive and very difficult to apply evenly.

handymac: thank you very much for your feedback.

Surprisingly, the store let me exchange the pine unit for an oak-veneered one. So yay: no need to condition it, and no knots! :)

Now let's see how I do w/ this staining/poly-ing thing (so far, I've only tackled painting); I'll take before/after pictures.

Planning to start installing a new knotty pine floor - 748 sq ft of it.....I will finish it off by a dark stain. Recently my brother did the same thing however, I notice now that the knots have taken on a chalky finish which is very noticeable. How do I aviod that? And should I stain the entire area all at once or work in sections? I am afraid of getting too much of an uneven tone. Thanks