Telling people to google something is rarely helpful.
It's great that Google shows noteworthy results for you, but that's not necessarily true for somebody else, possibly years after you wrote the answer. Also, unlike you, the other person might not be qualified to separate the wheat from the chaff.
At least noindex the closed questions, SO :(
I always wonder why I get more duplicates as my top hit than the question SO left open as the "original" because it at least feels like those are what I hit far, far more.
...often, with slightly different terms used. So there's a very good chance a given search will find one of the duplicates rather than the original. This is an explicit goal: it helps searches; in fact, if you're not logged in and you land on an unanswered duplicate, Stack Overflow will redirect to the original.
Though it is sometimes, particularly if what the question raiser seems to be lacking is the right terminology to search for. In that case then "Basically what you are looking for is [short description], search SO or Google for [keywords] and you should find more details." is possibly the best answer you can give.
You might rightly ask "why not just include the 'more details' or some direct links in your answer" which in some cases would be the right thing to do, but often these questions are fairly generic or otherwise lacking in detail so you could end up typing out a massive summary of a large knowledge area, little of which turns out to be directly useful.