I have adjusted toe-in on several of my cars using a tape measure. It is much easier if your tires have straight grooves. I don't believe an alignment shop visit is necessary. Toe-in changes greatly with ride height, and torsion bars sag over time, so how long will the perfect alignment hold? It does take time, and back and forth to get the steering wheel centered. When done, my cars drive perfectly straight when I let go of the steering wheel on the freeway and I notice no abnormal tire wear.
Ideally, the wheels should be perfectly straight when driving. For a RWD car like ours, set ~1/8" toe-in, so when driving the slight play in the steering makes the wheels straight. You might set 1/16" if everything is new and tight. For FWD cars, you set slight toe-out since the wheels pull forward which shifts towards toe-in. You never want toe-out when driving since that makes a tendency to wander.