Beyond classical guitar strumming [rasgueado, which I never truly enjoyed as much as pick strumming], I never once learned a 'strumming pattern'. I learned 'patterns' by feeling and playing my way into a rhythm. When asked over decades, 'so what's the strumming pattern', I always answer the same...'down-up' [down-down is still down-up].
What the actual strumming pattern is of any given song is relevant only after you can make chord transitions with your fretting hand, while your strumming hand does not stop. If you can't strum and change chords without stopping, working on strumming patterns inhibits rhythmic development [by creating awkward motions or stalls]. And, how you work on them matters. When a strumming pattern is the primary concern [because it makes the song sound like the song], but we can't make the chord changes, I liken this to demanding to know how the motor of a car works, before turning the ignition. When we train beyond any given song, all songs [the chord rhythms], fall into the hands naturally.
We first train the motor by hitting down-up all the time [for one chord or simple two changes]. Hitting all the time is most that we can do. Over time, we get more complexity with our motor rhythms by doing less [missing].
To play different strumming patterns, we think in rhythms. Once we have steady, deliberate control of the changes [with contant motoring], we then have the opportunity to be musical [think musically]. We allow this to be natural. We never think in symbols when playing rhythm anyways. We strum. We get rhythmic. We miss when we feel there should be a gap. Overthinking missing ['what's the strumming pattern'], can produce some awkward motion, and non-musical actions.
Strumming patterns also change within songs, as drums do [beats, fills, etc.]. Strumming in different rhythms happens by doing, not thinking. And, there are many variables to an overall strumming texture [not just missing]. Variables include hit-miss, accents, ranges, changing elements, palm muting and palm mute bouncing, press-touch, etc. Micro-managing all of these variables is tedious, if not impossible.
We highly recommend using your musical rhythmic feel to strum what you hear, rather than counting things out and needing them written out in symbols. The only time, as a coach, that I ever write out strumming patterns is for students, when/if they ask [often to prove that it's not as effective as just doing it - it's a question of confidence].
You already know, intuitively, how to strum and create patterns. And, we can strum any song in any rhythm. Core idea: you know how to strum and create rhythms, so just be natural in your approach. It happens [when your strumming motion is natural & constant & you are confident]. You may want to take a look at The Mix in Strumming & Ground in Chord Connect.
This page used to house a bunch of images for hitting and missing. I consider them roadblocks to true rhythmic development. Students often get hung up on this point. Remember: we can play any song in any style or rhythm [universal, easy, actual]. We don't let the actual of any given song get in the way of our development. When we develop our strumming skills, we can play all songs, not just the first ones. Again, be natural & play by feel. It's the only way to play everything you hear.
Note: for studying Flamenco guitar, go to Spain, or find someone who's trained there. It's a specialty style that requires hermeneutical experience. Go to the source. On our site, we are primarily focused on pick strumming, though finger surfaces are included in the strumming system.
I'm hearing the question 'what's the strumming pattern' less and less and this is encouraging. The word is getting out.