That makes it easier. I'll tell you I've never used a sealer under spray nitro, but then again I've only used it with maple, other woods may be different. I've never used a spray poly, so someone else here will have to help you. I've only used a wipe on with good results.
I think what your asking for is a finishing schedule that involves:
1) Staining (It sounds like you've got that covered)
2) Sealer (Just need to know what kind)
3) Transparent Color with poly or nitro (you got this)
4) Top coat (As a car guy you definitely have this)
Welcome aboard, and I'd like to know how your project turns out.
I'm not going to do a search, but I think this was discussed before. Also, you might want to look into pore filler, depending on the wood, and research compatibility issues between different types of material you lay down on your wood. Good luck.
Edit: Just noticed mayfly's response