+1  A: 

Bluevision have a nice plugin for Visual Studio to do this for you. Last time I looked, it was free. (yep, it's still free!)

  • IntellisenseAttribute class allows you to specify members for which intellisense symbols will be generated.

  • Ability to generate default intellisense symbols for assemblies when you don't have access to the source code.

  • NEW Snaps right into the IDE so that intellisense generation can be automated during the build process.

  • Supports two visual views: Full Mode and Skin Mode.

  • Full source code.

  • FREE!

http://www.bluevisionsoftware.com/WebSite/ProductsAndServicesInfo.aspx?ID=9

x0n
+2  A: 

You should be getting this for free (default behavior of control). Are the references all in place while you are typing the custom control?

There is an attribute to hide properties from intellisense:

[EditorBrowsableAttribute (EditorBrowsableState.Never)]

Use the description attribute to provide additional help:

[Description("My extra helpful description")]

There are some other attributes that affect intellisense and the property explorer you might want to look up...

HectorMac