I forgot if you mentioned if you're making the scarfs through the thickness or across the width of the strip? Just my 2 cents about scarfing, and some photos:
I never got good results trying to sand scarf joints. It seems like too many things can go awry, and I have an instinct against sanding glue joints, anyway. Here's how I do it:
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Place a scrap at the desired angle, and clamp the whole thing together. Cut through with a razor saw.
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Glue & clamp.
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After a little planing & sanding.
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