My compost is extremely weedy. I know what I did wrong, but is there anything I can do about it. I don't want to use weedkiller. Would it help if I buried it under a layer of topsoil? I have bags of stuff that's been put through the shredder but there's a lot of longish strawy bits in it from pruning shrubs so I was going to put them on the compost heap to break down some more. Would they be any use as a mulch instead?