If you're hiring, youre not a genius or bill gates. Kindly write the cover letter in a polite way. Secondly, please don't ask so much un-required skills, even though you don't even have a need of it. Be professional, and rather than asking for skills, just explain the task to be assigned. Many hard working candidate who are legible for the job, just don't apply because they don't comes up with the list you posted.
And last thing, offering a job is not a big thing, so do feel yourself on the ground and request for quotation and give equalent money to the candidate for his work rather than bargaining or been unjust.
Note: you buy there #work not there #respect.