Almighty, what you mention could be construed as 'green handshakes,' but I really mention something more direct and more common.
Rarely happens to an elder visiting a hall to give a talk, but every C.O. that visits a hall gets greeted by the 'friends' and many of them directly put money in his hand as they shake it. Many put an envelope in his hand. Some make sure he knows who gave the green handshake, others just think it's so wonderful to have the full-time servant visit and give, thinking that he needs it.
Beyond the C.O., there is no doubt that a D.O. or a Zone Overseer visiting an area gets the green handshakes from the local elders and others that want to please him, kiss up to him, adore him. For a GB member to visit an assembly or convention and give a talk here and there at the local kingdom hall to justify sending him to Hawaii or France, you know many local elders and local members will want to do even more. I cannot imagine that anyone but an older pioneer would even consider less than $100 US in a card.