Hey Diogo. I’m also trying to write a post each week and although in the beginning I think I found a rhythm. I feel that this rhythm is super personal but here is what I have been doing.
During the week, while I have some alone time like on the bus on my way to work, is where my best writing ideas bubble up. Using Evernote, I compile the main points and how I want to cover them in the blog post. Because I always have my phone with me, I make sure all ideas stay written down.
Then during the weekend, normally Sunday, I look that all the information I gathered during the week and start writing.
This way I feel like I divide the work. During the week I plan/brainstorm and Sundays I write the post.
Hope it helps. Abraço ;)