My exotic approach for the small amount I do is using one of my wife's empty hair colour bottles with the tube from a WD40 can inserted snugly through the cap.
I used to fill the bottle with a mixture of 30W oil and Kerosene 25/75 approx. In use, I upend said bottle, gentle or not so gentle squeeze to get the amount I want and start work. I also sometimes just let the heat of my hand expand the air inside the bottle and achieve a drip feed when parting off.
Lately I have begun using, "Angels Breath tapping fluid" because I made some up and A, it works ok and B, it stinks better.
Still, as has been stated previously, it was the joy of making the Tuna Oil tub that was the aim of Joules in his original post.
Oh, and Angels Breath does work well as a tapping fluid. Strange, as that was its intended use.
To save you asking, Angels Breath as I use it is a mix of,
1 Part Artists Turpentine (Not Mineral),
2 Parts White Spirits and
3 Parts Olive Oil.