If a barrel shoots better slightly fouled then thats how I hunt with it. If it doesn't matter then I start out on a clean bore. All that is required to figure this out is clean the bore completely after final sight inand head back to the range to test. Should mentionprior to firing make sure to run a couple dry patches to remove an excess oil. Will find a POI shift with oil in the bore as it causes increase in pressure, so a good habit to get into removing it for safety and repeatable reasons. Assuming your hold and shot are true you can compare if the gun hits where you left it after sight in. The only shot I worry about is the first out of cold barrel so be it clean or slightly fouled this is where I do my hunting trial and error. I then run my normal 3 shot group after the barrel has come back to ambient temeprature to see how it shoots.

In most cases I start on a clean bore then don't touch it till after my hunt, besides light gun oil for maint. reasons during the hunt.