If you are over 10K lbs GVWR, you must chain up in WA even if you have 4wd when restrictions are in place. On ice, I would rather chain the front wheels (which is not reflected in my second link). On the rest, I would chain the heaviest drive axle (DOT assumes these vehicles are RWD in the second link). With a DRW setup there is no advantage to chaining up only the inside tire, so make life easier on yourself and chain the outside wheel. All the tires on both sides of the axle must be chained if you have more than four axles on the road (this is important for those that also tow FW's or BP's with triple axles).
http://www.wsdot.wa.gov/commercialvehicle/chain_req.htmhttp://www.wsdot.wa.gov/NR/rdonlyres/1BE3F4CB-6C4D-48DC-B954-F70CAC5EAA7D/0/ChainRequirements.pdfhttp://apps.leg.wa.gov/WAC/default.aspx?cite=204-24-050