The fuel that leaked out from the aircraft at times formed a visible puddle under the centre line of the aircraft. Ground crews were not too concerned as the flashpoint of the special grade fuel was extremly low.
The Blackbird had its own fleet of modified tankers, designated KC-135Q, that were able to carry the specific fuel that was required.
Another interesting point, the blackbird, tho painted black, actually changed to a dark blue colour at the top end of its flight envelope, this was again due to the extreme altitudes and speed.
The launch of a mission was usually done in complete radio silence. The pilot and control tower and chase car, used various communications techniques to get around the radio silence, this was to prevent 'big ears' from listening in. With nearly every mission, the aircraft was deployed over sensitive areas, the need for the silence was understandable.
In the end, i believe a hand held torch was used to give the pilot the all clear for departure.