"Bumping" old questions is perfectly acceptable, and even encouraged, when you have something new to contribute.
Unlike traditional forums, the Stack Exchange sites don't have any strange rules about interacting with old questions and no one is going to think odd of you when you do so.
Since the primary goal is to get good answers to questions, no matter how long it might take, there is nothing at all negative about sharing your knowledge. In fact, that's what you're supposed to do. If you post a helpful new answer, it's very likely that you'll earn a couple of upvotes for your trouble.
You might also earn some badges for this behavior (which is another clue that it's encouraged, as badges are generally only awarded for positive behavior). For example, the bronze Revival badge is awarded to people who answer a question more than 30 days later when that answer earns a score of 2 or more. And the silver Necromancer badge is awarded to people who answer a question more than 60 days later when that answer earns a score of 5 or more. Each of these badges can be awarded more than once.
Following the same rationale, editing old questions and answers (whether your own or someone else's) to improve them or bring them up to date is also highly encouraged. It will bump them up, mainly so that your edits can be audited by the community.
Do note, however, that only edits to the question (including retags), edits to any of its answers, and posting of a new answer will bump the question. Comments don't bump anything.
In fact, just by way of example, I did something very similar to what I think you're proposing here. It earned me a couple of upvotes—I don't think the question's topic is a very popular one. But it felt good to share what I learned, and at least two other people did find it helpful, so that's got to be worth something.