I just had to deal with 3 giant tree sap blobs on my dad's black E350 hood. I had no idea what I was in for, but luckily I had most of my detailing arsenal in my Forester.
Step 1 was to wash the car and attempt to clay bar the sap off the hood. This didn't work.
Step 2 was to scrape away as much of the sap as is humanly possible with my fingernails, knowing fully that I may scratch the paint in the process. It's okay, though, because I have polish and compound in my bag.
Step 3, after claying the rest of the hood, I put some Meguiar's Ultimate Compound (
http://www.meguiars.com/en/automotive/products/g17216-ultimate-compound/) on a yellow Uber compounding/cutting pad (
http://www.detailersdomain.com/5-Pack-Uber-Foam-Pad-55-inch_p_297.html), slapped it on my Griot's Garage buffer (
http://www.detailersdomain.com/Griots-Garage-6-inch-Random-Orbital-Polisher-Base-Kit_p_683.html), set the dial to 6 and let 'er rip on the hood for a few minutes. This took out most of the major swirls and after a couple more passes of the buffer, the sap was gone.
Step 4 was to further polish and then seal the paint. I had to buy some Griot's Garage One-Step Sealant (
http://www.griotsgarage.com/product/one-step+sealant+16+ounces.do) since I forgot to bring my Sonax Polymer NetShield with me.
If you're thinking about wet sanding the sap, make sure you refine the sanding marks (start at like 1500 grit and move up to 3000) and use an aggressive compound to get the sanding marks out. There's nothing worse than unfinished wet sanding marks.
Note: I'm only including product links so you know you can do this, too. I'm not a professional, this was just my process and the products I used to get the tree sap out of the hood.
