Well the main goal of suppressive fire is basically to keep the enemy "pinned down" - preventing them to shoot, move and observe the situation. Machine guns and artillery are used to suppress the enemy with good effect. How does the suppressed feel - well depends of his own physical + mental conditions, training and what he is supposed to do. Most will tell you that they were seeking for hardcover, keeping their heads down and after a certain time trying to get back the initiative or figuring out how to stop the suppressive fire or how to leave the area. Some may have shaking hands and temporarily deafness until the "surving instinct" kicks in. This certain time of panicking isn't for everyone the same and doesn't depend on the rank/medals/achievements or marksman skills - one recovers fast, the other needs some seconds more and another just needs to be shouted/yelled (or kicked/pushed) at. Of course you cannot train for every situation but you can train to keep this panicking time as short as possible and get back to the mission. Imo good and believable suppressive effects are sound of bullets + impacts + explosions, orders shouted from TL, swearing from teammates and increasing "plings" of bullets/ricochets very close to the player. No need to have the vision stylish blurred, splattered with blood or dirt or even pulsing eyeballs. Let the player get his head or ass down on his own instead of forcing him into a color/camera sfx trip.
