Best way to clean carseats?

I’d like to ask advice on how to clean puke out of one particular area of my sons car seat. I already know not to submerge the straps or actual seat in water. I’m washing the padding and air drying that and Ive wiped the harness down with a damp rag and gentle soap. He did not get any puke in the buckle but the problem I’m having is getting the puke out of where the buckle connects inside the car seat. His harness and buckle do not detach from the car seat. And the owners manual does not give any instructions on how to clean in there. Thanks.