This is one of THE best tips I have learnt in all my years painting and I can't believe I only found out about it last year. It works for tubes of oils, acrylics and watercolours.
Do you hate it when your tubes of paint get all gunged up round the lid and screw thread until it is almost impossible to screw the lid back on. Or worse you thought the lid was back on perfectly but when you next come to paint realise that air has got into the tube and the paint has become hard and unusable and it has to be thrown away - aaaargh what a waste! But no matter how hard you try you can't squeeze paint out of the tube without leaving some protruding from the end which little by little builds up until you have a dried paint mountain to deal with.
So my genius and very simple tip to prevent this from happening is to always squeeze from the bottom of the tube, then when you have enough paint squeezed out onto your palette, just lightly pinch the tube about halfway down and the vacuum created just sucks the paint back into the tube leaving the end and thread completely clear of paint.
I can't tell you how happy I was to learn this simple solution after years of messy tubes and wasted paint! It maybe that you have known this all along and are wisely nodding your head or tutting in disbelief, if so I am pleased for you. But I feel I can't be the only one who was in the dark can I? Now I know why my husband gets so exasperated at my toothpaste tube squeezing technique, which is from the top of course!