Ok bare with me here. You can start this on any fret,and its good to do them on all frets,but for now will start with the 7 the fret.:
Place your index finger on the 7 fret, middle finger on 8 fret,ring finger on 9 and pinky on 10 fret. Not so bad huh.
So now you have all four fingers placed on the low e string. Now place ur index finger on the 7 fret of the a string,while keeping the other 3 fingers planted on the 6 string . now do the same with middle finger drop it to 8 fret on a string. Ect one finger at a time.the key thing here is to drop one finger at a time,while the others fingers remain on the string above.
You can do all down strokes.
Its a great exercise for dexterity finger strength.
Keep in mind you need it to sound clean ,no muffles.
Have fun and i hope i explained well enough. Cheers!
