I know this post is old, but I was looking up straining on here tonight, because this issue concerns me as well. I find that Metamucil is extremely helpful. It makes the stool thicker, which makes me need to strain a lot less and also makes it easier to pass gas, which can be difficult for me.
I've noticed that a lot of people seem to prefer having thinner stools because they feel that makes it easier to go. But I don't understand that. For me, the thicker and more solid it is, the easier it is to go and the less I have to strain. It's like when it's solid, the sphincter muscle has something to grip onto. It's like the difference between trying to pick up water with your fingers vs. picking up ice cubes.
I think this problem happens because the small bowel doesn't have the same kind of muscle actions that your colon has, to push out the poop when you're ready to. Instead, you only have your sphincter and outer abdominal muscles to compensate. I find that it helps to get off the toilet and walk around for ten or 20 minutes to go do something and then come back for a second time. And I always push in my lower abdomen with my hand to help move things along. It gives the muscle something to push up against, which is helpful.
If you're going to do the Metamucil, start with two glasses a day and increase it to three, if two is not enough. You have to find the right balance. If you don't drink enough of it, then it just won't help. But if you drink to much, it will actually make you have to poop to much. So you have to experiment and find the amount that works for you. Two-three glasses a day is usually enough for me.