For the initial clean-up, you don't want to be doing it manually, especially if you have lots of tweets to delete because Twitter makes it a really tedious task.

There are online tools that do just this, without the need to download anything, but then you have to trust a 3rd party app.

It is a bit of friction.

There are online services that do this much easier. Doing it manually is a big pain using Twitter's UI. I had around 20k tweets before I ran this and I wouldn't want to keep doing it periodically.