Spoilers are used for a very specific purpose, and slowing down a plane for landing is not that. When used the spoiles raise up and disrupt the airflow across the top of the wing. The result of this action is to remove any lift that the the produces, in effect it causes the wing to stop flying. If this is done on a landing approach it will most likely cause the plane to crash in a very ugly way.

You most often find spoilers on gliders where they need to "spot" land. They will approach the landing and remain a few inches off of the ground and then when they approach the spot they want to land in they will raise the spoilers which will cause the lift to cease the glider will land on the "spot".

So in practice, trying to use spoilers to slow down a plane for normal landings is a bad idea.  The best way is to learn to slow the plane down properly for landing.

Ken