I always store the guns with an antirust lubricant. Therefore, when I pull the gun from the safe I always run some dry patches down the barrel to remove and oil, lubricant, etc... I have tested shooting my muzzleloaders fouled and unfouled. My guns shoot better without fouling the barrel. So clean and dry is the best way for me to go.

It is not a tool, but the main thing I try and do is make everything consistent. Loads, bullets, cleaning procedures, loading, etc... Everything the exact same from shot to shot. That way if I change on little thing I should be able to easily know the results.