Q:

Need to repaint my exterior, a couple of question with painting

My exterior need a re-painting, I have got a couple of question here:

How do I find a paint that matches my exterior? Using naked eye is bit unreliable.
Do I need to scratch the old paint off before re-applying new one?

A:

If your goal is to touch up sections without a whole house painting...
In an inconspicuous area, use a razor blade and skim off a small section.  Take it to Home Depot and let them use their paint matching machine. Then have them mix an exterior paint for you.
I did this for an interior wall once and I could never tell the difference after it dried.
I would scrap and prime the bubbled portions of the wall.  
My 2 cents

