First I made a report showing the shortage of applicants over the last years using the "referral program", and how that affected the company productivity and Labor turnover rate
And since the company is already short with employees so recruitment from inside might be difficult unless the company has other branches to transfer employees from. If company can hire employees internally it will be inexpensive and less cost
Second choice is by external hiring using one of these methods, depending on the budget of the company:

a. Using the applicants who apply directly to the hotel; people who come to the hotel and drop their C.V, and this strategy is inexpensive.

b. Using employments agencies, but it is expensive

If the Director of H.R. is looking to save money in recruitment, than hiring from inside is the best choice if it is possible

Good Luck
Dr.W