Most overhead press exercises performed with a barbell rely on healthy rotator cuffs. Dumbbell pressing is easier on your rotator cuffs, but it's not as easy to go heavy (standing) because of the inherent instability of the movement. It can also be a hassle and energy drainer to get the dumbbells to the starting position, whether you're doing them seated or standing.
What you want is to reap the benefits of the friendlier-to-the-rotator cuffs wrist position afforded by dumbbells. This little bit of external rotation when pressing can be a game changer for shoulder health and comfort. Also, eliminating some of the instability goes a long way in making an overhead press comfortable, yet effective.
Okay, So What's the Solution?
Trap bars offer a perfect solution. And using them for a Z-press pattern is especially advantageous – it checks the boxes for proper and safe overhead work while still placing plenty of demand on the trunk musculature for stability.
You won't have as much propensity to overarch when you're sitting since your pelvis will be slightly more posteriorly tilted. When you're sitting tall, you'll encourage a neutral spine for a safer, healthier pressing position.
Also, holding onto the low handles of the trap bar enforces a neutral grip and the cradle clears the face (so you can actually position your hands in line with your shoulders). Since the cradle is one big piece, stability issues are a thing of the past, meaning you're free to load up heavy.
Set the trap bar on the safety supports at your desired height – a couple of inches below shoulder level should let you achieve a full range of motion.
Some lifters will have the mobility to set up flat on the floor with the legs straight out in front of them. Others, however, may need to make a couple of modifications to their setup to ensure proper spinal positioning. If you lack sufficient mobility or flexibility, simply raise your butt off the ground a bit by sitting on a plate, platform, or some stacked mats.
Bend the knees slightly and keep a shoulder-width stance. Sitting too narrow asks a bit more of your mobility, as does sitting with straight knees.
Depending on the size of your trap bar cradle (and the width of your squat cage), you may need to set the plates up wider than normal so that they clear the safety supports. And don't forget to account for the fact that many trap bars weigh significantly more than conventional 45-pound barbells.
I've personally seen trap bars weigh anywhere from 60-80 pounds, so don't feel like a weakling if you're only able to add quarter plates to the bar for your sets. Besides, what matters the most is the training effect you receive from the movement, and if light weights feel humbling, you're probably doing something right.