How to autofill a column with multiple values
1) Select the range B2:B5000 (or whatever your exact range may be)
2) Press F5 (Go to, Special, Blanks)
3) This should select all blank cells in the range with the active cell in B3
4) Now, in =B2 and press Ctrl-Enter
Edit: 4) Now, enter =B2 and press Ctrl-Enter
5) All blank cells will now contain a formula pointing to the cell directly above it.
6) Copy column B and paste as values on top of itself if you don’t want to keep the formulae.