How many times have you tried learning strumming by reading things? We all have. How much have you learned from it? To be honest, I havn't learned a thing. All i have learned until today, is by my ears and by my ribs.
When you turned the bass to full, when you boast it even more and put the volume as high as your speakers can play. Once you do all that, you can then feel the beat in your ribs. Play a rap song in Winamp, open your EQ (Equalizer) section, and load the "Full Bass" present. You hear that beats as a buzz, maybe cause you don't have subwoofers. But if you listen to a song like that, you will understand the beat.
When you're listening to a song, can you listen to that noise of a shaker in the background? Can you listen to that fluet being playing in the background? Can you listen to all the other instruments used. Just how all these instruments are played at a low volume, the Bass is also played at a low volume. Strumming of a song without guitars is (in my vision) played on Bass.
Whats all this bull****? How many have you listen to the song "Dil Nai Lagda" by Aman Hayer? The strumming of that song is based on its beat, but not exactly.
When you're strumming, you aren't following any book. When you are strumming, you are free of all books. When you are playing tabs, then you need to play it as many times as it is writen, but when you are strumming, you are a like a free bird. If the strumming pattern is, " D D U D " then you can still play " D D U D, D D ". There isn't any restrictions. Strumming is all about playing how your hand moves. At times you just need to listen to the song, and strike your right on your lap, as if you're playing a table. Once you get the strumming pattern as tapping (from your right hand). THen its all a matter of configuring the chord and their timing. Then just play with the song.
If not clear, then ask.