Thanks again as always Muzikman.
I sprayed it sooo much but what I found is that even with all the big chunks of mud are gone and it seems to be clean but when the water dried up it starting to show the white clay-ie stain everywhere.
It's not the actual mud anymore but it's actually mud stain.
I will try out the Simple Green, but I pray I don't have to scrub.
You guys got it pretty cheap down in US for car washing... here you can't find any self car wash place take less than $1 and it only give me 1.5 minute. If I didn't have the pressure washer at home, I would probably have spent $150+ just for spraying all that water for 4 hours.
I am definitely staying out of mud from now on, but I need to get rid of these mud first. Nasty stuff.
EDIT: I think I found the stuff I need here