Hi Maestro,
hmm, that "shine" I am also looking for since forever. I would recommend to get the UAD (The SOLO card would sometimes run at 200 USD). You can test-drive all plug ins for a period of time. Try them. You can start with the Neve emulations. But the problem is with mastering plugins: In the beginning, except the presets, you can do more wrong than right. It is an endless process of listening and trying.
If you get a dongle, you can testdrive Waves as well (as I recall)
I heard also, that SSL is still another good start, not sure about the test drives.
I also looked at mastering classes on a remote level: Yes, they are there, (for example Berklee) , and they will give you the basics. But you need to learn to listen and work with it, and that is only possible on site. (For example, SAE)
Also, I have very good results with voxengo. They are also used in a lot of top studios. I only retired their Convolution Reverbm because it is not 64bit and it sounds too much like tin. You can testdrive all their products easily.
Like you said: Beginner's fault (like my recordings) ist most often to overdo everything: Too much compression, too much reverb, to much "in your face". To lern the "slowhand", the subtle notions, is really hard.