It usually depends on the time of day. But then again there can be a ton of traffic at really odd/random hours also. It sounds like you got stuck in the rush-hour traffic though unfortunately. That can be a bitch. Express lanes can be hit or miss. If there is an accident on the main lanes, then yeah, Express is the way to go. But then again sometimes there can be accidents in the express lanes, so then you're screwed. Generally though, i'd probably stick to the express lanes.
The best times to travel are late at night, or sometimes the late morning hours can be good too (10-11am). Traffic around Everett is almost always bad due to Boeing, so i havent found any tricks for traveling through Everett, and i've been driving back and forth between Seattle area and Bellingham for the past 8 years now.
As for any tips, just try to avoid traveling to or around Seattle on game days, or between the hours of 7am-9am and 4-7pm Monday through friday