couple of options here, I have done both.

1. Shoot .38 specials in your .357 and clean the gun as well as the cylinder.

2. Load the .357 case with the top end load listed for the .38 special load.

Been doing this for 40 years now and never had an issue. Used to shoot a lot of .38 through the model 19 for matches when I was an LEO, cleaned the gun well and never had any issues.