I remember getting Tubasti glue all over the place back in the 70's, but I didn't use sew-ups much and my technique needed some refinement.

In more recent times, I've had good results with the recommended process of applying glue to the rim and tire, waiting for it to get tacky, and then mounting the tire. With that method, there's no liquid glue to move to the wrong places.
Disclaimer: my experience with tubular is nowhere near as much as some of the folks here.

Steve in Peoria