You said people entering your house remove their footwear, but still carry dirt on their socks - you may try giving them a pair of shoes to use inside only.

This way even if they have dirt on socks, it will remain inside the shoe. Once the person stops using them, you can wash them in the washing machine. Look for shoes made of cloth or some other washable material (I've seen this kind is often used around Europe - also have them at home and you can easily wash them and they are really cheap to buy).

You said people entering your house remove their footwear, but still carry dirt on their socks - you may try giving them a pair of shoes to use in-house only.

This way even if they have dirt on socks, it will remain captured inside the shoe. Once the person stops using them, you can wash them in the washing machine. Look for shoes made of cloth or some other washable material (I've seen this kind is often used around Europe - also have them at home and you can easily wash them and they are really cheap to buy).

Take note, some people consider that the practice of giving your guests shoes is rude.