So, i saw this (https://us.v-cdn.net/5021068/uploads/editor/5n/ic034pkeexlo.gif) on polycount, the guy was using booleans and the bevel shader, i tried to do that, but there is something that i am missing, when i try to do that, i end up with bad shading around the holes.
Show us the mesh please.
Clean up your model with the knife tool. Try to keep quads. Split your edges using autosmooth set to 180 and mark the edges around the Boolean sharp. That should take care of the problem. That’s how I make Booleans work for me. If you want you can add a bevel modifier but you may have to adjust the bevel weights to prevent other shading issues.