Today it’s a lot different. The fingertip (your index and ring fingers only go in to the first knuckle) resin reactive balls are more efficient for getting strikes but will leave a lot of ten pins or seven pins if you’re left handed. This is because the ball enters the pocket (1-3 or 1-2 if you left handed) at a sharper angle causing the 6 or 4 pin to fly around the 10 or 7 pin. Now this where a spare making plastic ball comes into play. I personally use a plastic ball to make all my spares whether they are on the right or left of the lane. I revert back to the day when all balls were alike and had to throw straight at whatever was left. It makes sense that less hook the more chances a bowler has of making that spare. My plastic ball is drilled fingertip just because it’s easier to throw. I don’t think that flip flopping back and forth between a conventional and fingertip grip is a good thing.
The industry has come a long way since I learned how to bowl. The equipment is better but the fact remains the spares haven’t changed. The formula for a great game is to make your first shot a good one so the spares you leave are one pin spares. Strikes will happen on their own and making your spares will drastically improve your score. So my advise is to get yourself a plastic ball for those spares and practice, practice, practice.