nose picking...

i'm getting very frustrated w/ DS & the nose picking. I know little kids pick noses, and over time they learn not to do it, etc. However, he used to pick so much he got little scabs inside his nostrils & I had to put antibiotic ointment on...then it got a little better but in the last month he is now in the habit of shoving both fingers up there at the same time, what seems like all the time though I am not sure he does it at school very often (like other behaviors, biting nails & sticking hand down the back of his diaper, he seems to only do this at home). This morning his nose is bleeding from one nostril, often he literally has 2 stripes coming down from his nose b/c of dirt from his nose/fingers/mucus, etc, it is really gross. We talk about how it is dirty, it can hurt him, shares germs, etc etc. I try to go between not making a big deal & addressing it b/c I just don't know if I want to focus too much attention on it. We don't yell at him or anything, just usually say please take your fingers out of your nose, or even just, "DS-fingers, or please stop picking your nose, it is hurting your nose, etc... He is always saying (like this morning after the bleeding) that he won't do it anymore but he's 3 and welllwe all know how that works out.

any tips?