Couple of issues. First, the ring terminal still has a significant amount of corrosion on it. If left that way, it will gradually creep underneath anything you put on top of the bolt. It would be best to replace the terminal now while you’re working on it. They’re cheap and it takes minutes to do.
It’s hard to tell if they are there but best practice would be to include a star washer on either side of the ring terminal to bite into the adjacent surfaces. Face contact alone will fail much faster than if you use a biting washer (split, toothed).
The ring terminal crimp is left totally unprotected. If you’re lucky the wire is tin coated copper strands. The act of crimping often disturbs the tin enough to expose bare copper that can/will oxidize rapidly in this environment. Naturally bare copper will oxidize really fast. The crimp joint should also be protected. This can be done with a top coating or by using a heat shrink with sealant.
The plasti-dip cover most likely will not stay put by itself if you pry it off and apply grease in-between. The cover is formed to the exact shape without grease. The grease will space it off the bolt/terminal.
There are top coatings that do what you want. Fluid Film is one. Once the grounding point is completely clean and mechanically sound, you spray the FF over the connection to protect it. It won’t be as messy as dielectric grease and be less prone to collecting significant debris over time.