You're too impatient. White vinegar alone should do what you want, and its slower pace can give you more control over the process. How long did you soak?
I've mixed a squirt of 3% peroxide and a squirt of vinegar and then applied the mixture to the front of the coin. The results are pretty fast, I know I am impatient
I tend to be impatient, so I go with a 50/50 mix and watch it closely. The advantage with pure vinegar or mostly vinegar solution is that the etch is finer...not as harsh to the entire coin's surface. Which improves appearances. Fun to see that some semikey/key Buffalo are still in circulation. I was surprised to find many of the early D and S mint marks here on the East Coast for my Pickled Nickel collection. S mint marks are harder, and a few are still missing. Given I haven't CRHed in 6-7 years, it explains why those slots remain open.
I think that's correct. I generally use a 2-step approach. First, the harsh 50/50 to find a date and/or mm. If it's one I need, then I do the second step which is either a very week solution of peroxide/vinegar, or straight vinegar. The finish is smoother and the reveal more defined. Sometimes the harsh reveal indicates a coin is too worn, so doing step 2 is fruitless.
These are the pickled nickels I pulled from circulation during CRH events. Some interesting finds floating around out there.