I find this forum very usefull so why not ask another question?

I play mostly punk rock like pennywise etc but palm mute parts, which I adore, sound very scratchy, I mean that the sound of the pick touching the strings is loud so it doesn't sound nice. What do I do wrong? I keep my right hand on the bridge. Results are worse for A string, less in top E.
Another problem is the upstroke palm mute, I can't get it sweet, playing a power chord I find it hard to play all three strings at once in palm mute.
Does anyone know a SIMPLE guide on the internet for fast up & down stroke palm mute?
Sorry if I said too much...
Its difficult for me to visualize where your hands are. I suggest maybe moving your hands down close to the bridge so the strings have enough slack to still vibrate. Make sure you are fretting the notes as if you were playing them open.

Only thing I can tell you for fast up and down stroke is to just practice until you can do it faster.
You need to slow down and work on your technique. Also turn down the volume on your guitar and use more gain or an overdrive/boost pedal to eliminate some of the pick noise. And if you’re using hard pointy jazz picks try something bigger and softer for your rhythm playing.
could it be the way you hold your pick. I get the same thing sometimes i slowdown a lil and grip the pick better.
Why pluck just one string when you can...

Palm muting's all about technique. I play mainly metalcore type stuff, so I palm mute a hell of a lot, and know what works for my guitars. For each guitar and each pickup, the position your hand needs to be in is slightly different. Try moving your closer or farther away from the bridge. Also make sure that the side of your hand is muting all the strings you want to play.

People above have said flat picking, and I guess if that works for you, then do that, but I always use the side of my pick. I have to, because I tremolo pick palm mutes, and that's pretty much impossible to do with the flat side. When you're doing triplets and shit, you don't want any resistance like that.
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check out the technique forum, and make sure to read the stickies. havent been in there in a while, but i think there were some links that could help you out.