There isn't really a way to add skills to the call while it is waiting in queue. The ideal goal of the callback is to keep the caller's place in queue and call them back once their spot is reached. In theory by wanting to add a skill to limit the number of agents that can receive the interaction, that is not necessarily the goal you wish to achieve.
What you could do, is in the in queue flow where you are prompting the caller if they would like a call back, instead of setting up the call back in the in queue flow, you can use the transfer to ACD interaction, transfer back into the same queue, add your callback skill, and use a different in queue flow that only has the steps to set up the call back. This will alter the position in the queue for this caller though.
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Jason Tripp
Independent Health Association, Inc.
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