关于逻辑中的双重否定句式含义的快速理解

flyhigh2016

先上两个例子，应该都是prep中的逻辑题目，题干就不放了，就放答案中的句子：

Few if any of the RDS radio stations that began broadcasting in Verdland after 1994 broadcast to people with RDS-equipped radios living in areas not previously reached by RDS stations.

Makers of cookware will not find Kitchen a less attractive advertising vehicle because the magazine's name is associated with a competing product.

虽然知道双重否定就是肯定，可是每次读到这种句子，都要反应半天，请教下大家，有什么好的办法来快速理解这些句子么？另外他们用这种双重否定句式比直接用肯定句式有什么好处么？是想要强调什么么？