How to wash an old soft toy?

I have an old soft toy from my childhood that seems to be permanantly grubby. The last time I washed him made no difference. His label says he's surface washable only. I've heard people say that you can put surface wash only toys in the machine anyway, in a pillow case, but this toy is irreplaceable and I'm not going to take any risks with him at all. So I was wondering what is the best thing to wash him with to get him as clean as possible and make his fur a bit softer. Washing powder? Soap? Shampoo? He's made of polyester fibers and plastic pellets. And should I just air dry him?