Estate Planning for non-US citizens or residents

[FOP]

Hello,

I'm an accountant situated in North Vancouver, Canada.  Many of my clients are high net worth individuals, and many own a 2nd home in the US.  I am currently assisting the Executor, on his father's estate issues, and he requires the completion of both the 706-NA form (federal) and a Washington State Estate return, and he's likely going to owe tax at the state level, due to the lower exemption.  Although, I've pretty much prepared the Washington State return manually, I would prefer to have access to either a software program or someone whose more familar with filing this type of tax return than I am. 

I would appreciate any assistance one may have to offer. 

Thank you,

FOP