how to flush sediment out of my water pipes
There isn't an easy solution for this.  Normally if you think there is a huge sediment problem then you need to contact local water company.  They will probably unhook your meter and then cut your pipe somewhere near where it enters your house.  They will then used compressed air to blow all of the sediment out.  

My local water company had to do this a few years ago.  I noticed a huge decrease in pressure after they did some "construction".  It took them about an hour and there was a noticeable difference.  Now if there is sediment (less common) in the pipes in your house this is the same process except much harder.

Basically you have to isolate each branch and clear the branch of water.  Then you need to make sure there are no filters anywhere that would catch the sediment.  Means taking out shower head, disconnecting all sinks (hoping you have shut-off valves), taking filters out of shower valves... It would be an all day project for a plumber and there might not be that much gain.