Use a copier to enlarge the handwritten font to the size that fits your sign. Print it.
Cover the back with graphite (use a graphite stick or a regular pencil). You can also use a sheet of graphite paper instead.
Tape the paper where you want the words to appear on the sign.
Trace over each letter, pressing hard enough to transfer the lines onto the wood.
Go over the lines if needed, then begin painting.
If you prefer, use paint pens to form each letter.