Installing a new bathtub during the week end, I only needed to screw in the drain.
I had already experienced breaking the old drain when i removed the old tub using needle nose pliers and chanelocks.
The tub's installation manual also mentioned not to tighten the drain too hard or else risk cracking the fiberglass ;8(
I didn't want to go out to buy a tool i'd only use twice maybe!
So...

Step 1: Tools and Material Needed:

- A saw, I am fortunate enough to have a compound saw but a hand saw would work as well.
-Chanelocks
- About a foot of 1" PVC
-Plumber's putty
-5 to 10 minutes

Step 2:

Cut 4 evenly spaced 1' slits on the lenghth of the end of the PVC. They should be spaced to fit in the drain.

Step 3:

Check that it fits snugly and make the necessary adjustments

Step 4:

Before you start screwing in the drain, don't forget to make a nice ring of "plumber's putty" between the tub and the drain.
Tighten with an adjustable wrench or chanelocks and clean up the excess putty and voila.
I could have made a more elaborate tool by adding a cross bar instead of using a wrench to tighten.
The size of my drain is pretty standard and 1" PVC was perfect. You may need to use a different size for your own customized tool.
I am also aware of the fact that there is a tool that does just that. However, this took less than 5 minutes to make and that beats the hour it would have taken to get out, drive to the big box, fork out $10, drive back, use said tool just once.
Your questions and comments are welcome!