Painting is NOT my most favorite thing. (Neither is sewing, but I like the outcome/finished product, so I do it anyway). But, I will tell you all I know about painting furniture.
I have painted a dresser, bench, chair, mirror, sofa table, stool, kitchen table & chairs, and a little shelf. The only thing that I sanded and primed was the dresser. Everything thing else... I just slapped a coat of paint on it. I have used the same can of white paint too.
Sometimes the ultra pure white was a little too bright, so I toned it down with a little bit of that oops paint. But I love the shine of the semi-gloss. (Flat paint is just WAY too boring!) I used a little roller for the dresser and kitchen table because they both had large flat surfaces, but I used a good quality brush on everything else.
I have only used about a quarter of that gallon of paint so far. As for the paint colors inside of the house?... the house was already painted when we moved in. Lucky us!