This is the solution I arrived at.
A sleeve for protecting the arms when grinding is used as the sleeve over the grinder exhaust air port.
Here is the previously troublesome air port which blows oil all over your T-shirt - or mists your visor in a second it you catch that direction.
Constrictor Knot at front holds sleeve in place just behind hand-grip part of die-grinder.
Like this - this is how the Constrictor knot is used. Put the sleeve on inside-out full length along die grinder. Tie Constrictor Knot at midpoint, butting up against shoulder where air-motor ends and smaller end "handle" area begins.
Then fold back on itself halving length at the Constrictor Knot.
Here is the die-grinder running. Sleeve inflates at low pressure. Can hold die-grinder at any angle of rotation - direction of exhaust port is now irrelevant. The 2 layers of sleeve between the air exhaust and the outside world stop the oil mist.