The character ὖ in the word οὖν from Matthew 6:2 was causing me all sorts of fits. I eventually went into Microsoft Word where if you use the Insert Symbol dialog (or type ‘1F56’, select it and press Alt + ‘x’), you will get the right character. It appears that the polytonic keyboard layout lets you do the circumflex/tilde with breathing over α, η and ω, but not ι or υ.
Nope, further experimentation based on my incredulity at the pain I went through caused me to stumble upon the right key sequence. Hit the ‘=’ character followed by ‘y’ when in Greek Polytonic and you will get the desired character. And Shift + ‘=’ followed by ‘y’ will give you the rough breathing version (or think ‘+’ followed by ‘y’, same thing).
My issue, just offhand, was that I kept either using the Alt key (which is commonly used to add iota subscript/adscript, an impossibility for upsilon) or using the Shift key, which is used to toggle into a rough breathing (and I wanted smooth). Or maybe worse, I did both, which resulted in ῟υ. Not at all what I had in mind. The restriction crossed out above is for cicumflex/tilde with breathing and iota subscript/adscript combined, which is only valid for α, η and ω.