1. Funnel. For something like the light lotion, a funnel should do nicely. For something thicker, it might not work so well.
2. Piping bag. I buy disposable piping bags from the cake decorating shop (or Daiso, if you're lucky enough to live near one!) and use that to fill the bottles. If I only cut a small snip in the bottom of the bag, I get enough control to slow the flow as I get to the top. Some people use plastic sandwich bags for this purpose. I've never had that work for me - I make a horrible mess.
3. Syringe. If you're filling small bottles or need to fill the tippy top, sterilized one-use syringes from a local feed store are ideal. You can get them up to 60 ml (at least at my local shop) and this is perfect for a 2 oz bottle. You don't need the needle part, and you can get ones with larger holes in the bottom. I find this is a great way to get the last little bit at the top filled for larger bottles as well. And you can toss them when done! I think I paid about $0.35 for my large ones and it's worth it - no clean up (excellent!) and good precision when pouring.
I find if I pour it about 3/4 to the top, then bang it on the table, I'll have to fill it a little more. Using the piping bag or syringe means I get it up the top well. (I don't sell, so I'm not worried about weight, only about appearance. For those of you who sell, I'm sure you have to worry about the weight of the product!)