Im learning by the way by RHCP, been trying to teach myself for about a year so might be doing it wrong but when i play the scratchy bits I hold the strings with my fretting hand and try to play the muted notes like this.

Even though ive got a good hold on the strings i still get a buzzing noise when I scrape them. Ive not tried palm muting because when watching John Frusciante play is picking hand allways seems so free and loose so just assumed he was using his fretting hand to mute the strings.

Have I got this wrong? is there a different (better) technique or does it just require more practise?
What do you mean by buzzing? Are the strings actually ringing out? Are you getting harmonics? Try doing both palm muting and left hand muting.
Quote by Geldin
Junior's usually at least a little terse, but he knows his stuff. I've always read his posts in a grouchy grandfather voice, a grouchy grandfather with a huge stiffy for alternate picking.
Besides that, he's right this time. As usual.
Be sure you have all your fingers muting so you don't have a good chance of hitting harmonics, and also make sure you're not pressing too hard, you might be half-fretting a note where it's not fretted but not muted so you get a buzzing sound.