When I get ready to press out tinctures, I use a ladle to get equal amounts of macerated herb and alcohol float from my tincture jar to the press. Since we do most of our tincturing in gallon jars, a kitchen soup ladle works great. For smaller jars, such as 1/2 gallon and quart jars, a large kitchen spoon works great. Just tilt the jar a bit when scooping the goodies from the tincture jar to your press.
BTW, the only time I use a baster is when I am filling dropper bottles of pressed tincture.
There really is no 'correct' way to do it. It's just what works best for you and what ever tools you have to do the job.