You don't have to use *.RESX resources manually. This code is already generated for you.
Look at the auto-generated .CS file in a child node of your *.RESX node. Locate the auto-generated static class and its static string properties named after your string resources. Use them.
This way, you never need to use resource names. You would need to support string constants with the names, the compiler cannot check if they are valid or not. Why doing so if the .RESX file also has these names. It would be a violation of Do Not Repeat Yourself
(DRY) principle, see http://en.wikipedia.org/wiki/Don't_repeat_yourself
]. Auto-generates resource file makes your project maintainable.