Hi, there. I'm happy to give my 2¢ on this.

What's tricky about this is: some educated people out there use correct grammar 100% of the time, and can easily tell when sentence is not grammatically correct, but these same folks may be hard pressed to name the actual rule of formal grammar that comes into play. Ultimately, the point is not to be able to name the rules, so much as to incorporate them seamlessly into your own writing and into critiques of the writings of others.
With that in mind, here's what I would recommend. As you practice SC, insofar as it's possible, jot down a brief note for each question --- if you remember the rule, write some abbreviation of that rule; if you don't remember the rule and are just going on feel, write some symbol, a star or something, for that. When you are correcting your work, pay attention to several things.
= When you are just going on feel, not relying on the rule, how often are you right?
= When you think you are applying the correct rule, how often are you right?
= Are there any rules, or any situations, that time and again you fail to recognize when they arise in context?
Knowing whether the majority of your mistakes come when you are not remembering the rule or when you are applying what you understand as the rule --- knowing that would be a huge piece of data for your self-understanding and preparation.
Also, seeing if there is some kind of grammatical pattern, for example parallelism, that time and time again you fail to recognize when it arises --- that would be an important indication that while you understand that grammatical rule in some formal abstract way, you haven't actually integrated an active understanding of that grammatical rule. In that case, I would recommend redoubling your efforts in searching for that grammatical pattern in an ongoing way as you read --- the WSJ and NYT are excellent places to stay informed while you bone up on proper grammar.
Finally, here's a free video lesson, part one of a unit on modifiers.
https://gmat.magoosh.com/lessons/615-modifiers-iHere's a free practice question --- when you submit your answer, it will be followed by a video explanation of the solution
https://gmat.magoosh.com/questions/1086If you find learning from video is more engaging, more effective for you, than learning from a text, you might give
Magoosh test prep a look. We have dozens of lesson videos on the verbal side, and dozens more on the math side, as well as hundreds of question, every single one with a video solution.
I hope that was helpful. Please let me know if you have any questions.
Mike