Sketchup itself is a great program but lacks many features. Fortunately there are thousands free plugins on the Internet which easily allow you to do nearly everything.
There is one plugin creator which deserve a special mention – Fredo6
You can find his latest plugins on sketchucation.com (you need to register there).
First you need to download a common library and instal it like a normal plugin.
Next you can instal any of the following plugins:
- Tools on Surface
In my opinion the best one are FredoScale, then Curviloft, RoundCorners, ThruPaint from FredoTools and GhostComp to handle heavy skp models.
Now you can do what Rhino can do or 3DS Max but easier and in more friendly environment. Good luck and have fun 🙂