I use my side project, MindAUX.
Creating Todos is pretty easy; i can create as many as I want at once via an email or entry in the search.
Categorizing them is the next trick: I get emails every other day for todos I created that aren't classified yet.
After that, they get regularly reviewed and timestamped as reviewed so they don't need to reappear for a while. I get emails for any todos that have never been reviewed, or that are overdue for a review.
When I'm deciding what to do in the next i select several I think I can tackle and add them to my list of active todos, then sort them based on priority.
Anything with a due date gets noisy (pesters me via email) as the date approaches as well as if its overdue; until it's removed or completed.
I could but haven't needed to use contexts yet or time estimates; primarily it's been a matter of making sure something is at least in the system and being tracked/reviewed in a way that I can forget about because I know it remembers and will remind me through a variety of ways.
I also get a weekly report of open todos, new todos, and other statistics.
This works for me, because it is easy to do brain dumps of this or that, while also making it harder for me to drop a particularly important ball, or lose track of it.