I am sure there is a guide somewhere... What techniques do you use to find the best ex-EU fares (in this case to the US)? My use case is:

Want to fly J to SEA from LON
Can leave from any reasonable EU starting point (DUB, AMS, MAD etc) but would need to position from LHR
Would also look at EU-LCY-JFK-SEA
Can travel on many days in April or May

Ideally I want a list of all options that fulfill these loose criteria ranked by cost so I can then rank by convenience. Clearly, using ba.com I would need to search many, many combinations which would a bit annoying.

I guess the answer is to learn the intricacies of ITA Matrix (which seems to be down at the moment)? Surprised that a more consumer-orientated travel website (such as Kayak) doesn't offer slightly more powerful tools to enable this sort of searching.

L