Alclad II is a 'paint' that is sprayed on to the piece. It has some important preparation steps, but the final result is quite amazing. It might take a bit of practice, but once you get it right you will be stunned how awesome it looks. It doesn't look like silver paint, it looks like chrome. You need an airbrush to apply it though, but I have heard that some people are successfully applying it to tiny parts just using a brush.
Murray
Try some of these threads which might give you a better idea about it.
http://www.finescale.com/fsm/community/forum/topic.asp?TOPIC_ID=4004&SearchTerms=alclad
http://www.finescale.com/fsm/community/forum/topic.asp?TOPIC_ID=1292&SearchTerms=alclad
http://www.finescale.com/fsm/community/forum/topic.asp?TOPIC_ID=1989&SearchTerms=alclad
http://www.finescale.com/fsm/community/forum/topic.asp?TOPIC_ID=6101&SearchTerms=alclad
http://www.finescale.com/fsm/community/forum/topic.asp?TOPIC_ID=1003&SearchTerms=alclad