If you scrape a brand new reed, it may be good for a while, but three months down the road it will die. Only scrape reeds that are broken in. For new reeds that are too strong to play, I prefer to pinch them to get a temporary reduction in strength. To pinch, hold the reed on the two (relatively) flat sides between the thumb and forefinger, about 1/4 of an inch from the top of the reed. Give a good hard pinch for about 2-3 seconds. Pinching makes the reed easier to play, but will sharpen the pitch. It's a lot easier and safer thing to do to make a reed playable than scraping.
Chanter reeds will get easier to play all by themselves if you play them for a while (about 3 weeks to a couple of months). After you've gained some endurance, you'll want to tolerate a slightly hard reed when it is new, because after several months it will be just right.
The best bet with scraping (if you just have to do it) is to scrape just a little, and then play it like that for a couple of days before deciding whether you need to scrape some more. The long-term effects of scraping are not always immediately apparant.
Chanter reeds also become easier to play with exposure to moisture. But since long term exposure to moisture results in mold and a dead reed, keeping your reed wet is not a long term solution. It may not be a bad deal to scrape a too-hard reed just a little, wet it with tap water, then try to play it for a few days. Saliva has acids that deteriorate the reed, so don't deliberately wet the reed with saliva.
To keep the moisture in your reed consistent (and mold free), always remove it from your pipes after playing. Reed protectors are good for this, as it allows you to keep your tune (you don't have to remove the reed from the chanter). A lot of top end players prefer to keep their reeds in a small sealed jar between performances. Plastic film canisters work good, always store 2-3 reeds together to keep the moisture levels correct. Be careful not to crush the tops of the reeds when putting the top on! That really hurts when you do that to a good reed.