Here is my advice on holes. I tend to go on the heavy side and have about 120 holes that are slightly smaller than an average pencil.
After some experience, I know that this is likely overkill. You may want to start with half of that and if you notice you have problems with too much humidity or odor from the tub when you open it, then add a few more holes at a time until things regulate nicely

Having less would likely be better due to keeping some of that extra heat in, and making sure things are humid enough, so start slow then reconsider if you think there isn't enough
For smoothing edges after drilling, I discovered an AWESOME and FAST way. What you do is take a straight razor <like the ones that you slide into the flat rectangular scrapers> and slide that puppy along the holes! It'll take all edges off in no time!
When making holes, here is another hint that works particularly well when small ones are needed. I use about three nails as thick as I need, then lay them on an stove element set on max <piping hot and red> then I use my forceps to pick a nail off the element and melt a few holes, then rotate as the nail cools and doesn't go in as smooth.
I tried every method out there for holes. Drilling, dremmel, soldering iron, heating nails with candle or lighter, etc. and have definitely found the previous tips to be GREAT!
Here is a pic that shows the holes I have fairly well. I don't put any holes in the fronts of the tubs.
Rebecca