I have'nt sinewed a lot, a dozzen or so bows. But I never cleaned any of mind only sanded them put on sinew. If you sand it's new wood why clean and had moisture. I had a friend CROOKETARROW that was half IROQIOUS that built bows for over 50 years. When he sinewed ,sanded is all he ever did also.
I made my glue like he made his glue, so it would BARELY more down hill. Add the sinew to warm water and glue made really thin. Leave it in for a little while to let the glue pentrate then pull between dry rags to remove the water and glue. Sand the bow with 80 grit sand paper. Seise the bow back with the thicker glue. Add the your sinew.
Never had or heard him say he ever had any problems.