Thank you both, Billy and manXcat.

[br]I didn't know the Shane Simpson's tutorial but this is the kind of approach-for-beginners that I had in mind when I first wrote my post. Although I fully agree with manXcat that strumming is learned for each specific song (and, yes, you are right, many songs tutorials devote some room to the strumming pattern), I still believe an overview of the most common strumming patterns, rules and related exercises within the Core Learning could help to lay down strong(er) basis.