If you seal the wood, dye isn't really going to work very well... When you add dye to your clear finish, you're creating what is essentially a toner and you head to your color with repeated spray coatings to build it darker. Spraying is essential to avoid streaking. And yes, if you add dye to lacquer, you need to be sure you're using a dye that's compatible. You can also add alcohol soluble dye to shellac if that simplifies things for you, but again, I recommend spraying for best results.

That all said, this concept of "blotching" is an interesting conundrum...because it's just the wood's figure taking color at different rates. Some folks don't prefer that figure "enhancement"; others of us embrace it. The challenge is to use material that's at least consistent so that individual components look unified when they come together as a unit.