Using an old half whiskey barrel as a planter  

I think you have basically answered your own question. My mother in law has one of those barrels in her front yard, and she has done all of the things you just mentioned. And it looks awesome. There is an added advantage to the rocks in the bottom, besides drainage...they make a good anchor for the barrel so it doesn't get tipped over. Even with all of the soil in it, my mother in law's would easily roll over if bumped.

yes drainage holes are great but not to big and drill them about 4 inches from the bottom. Gravel is also a good idea up to the holes. put in the soil and plant away!and yes white stones under it should look great!

You have the right idea. Drainage is must.To put some pebbles in the bottom of the drainage is a good idea

That is a good idea. My my part of Canada, we often use half a potato barrell, which is made from wood. I would suggest to, yes, drill holes in the bottom and to put gravel in the bottom for drainage as welll...just like a normal plant pot. Sounds pretty.

I would do both put in the holes and the rocks. I used to have two of these planter with strwaberry plants in them. They worked very well. I got quite a nice crop from them and they looked nice too.

My Aunt has several non-conventional planters that she uses to put outdoor plants in and they look gorgeous. You are doing the right things by adding drainage holes and rocks at the bottom of the planter as well. Plants need good drainage so that the excess water will drain out, and that makes the plant healthy and happy. I think that the white stone underneath the planter will look good and that's also a good idea. Happy gardening.

Linguist , I've heard of putting busted up pieces of clay pots in the bottom for drainage as well .

Yes by all means some drainage holes would be nice. I don't think it will hurt to put stones or rocks on the bottom for drainage but it really isn't necessary. Good Luck.

yes all that you mentioned is recommended, i used plastic barrels before and did the same things.

all this sounds like a good Idea. Even In combination.