How to update the stamps
First of all, you need to understand the two methods of multiplayer in Sword and Shield. By default, you'll be on Local Connect, looking for nearby players to connect with. Pressing Y will take you to the online menu and pressing More will switch to the Internet for connectivity. This is the essential first step in getting more stamps, and this is how players reach out to each other. Once connected to the Internet, your stamps will be displayed on the right. They should fill up somewhat automatically, and pressing right X could refresh them. However, the game likes not to offer this as much as players will surely want, so there are a few tricks that you need to use.
Once connected to the Internet, if no stamp is offered to you, you can force it a little by launching a surprise exchange. Select this option from the menu and follow the prompts. If you don't really want to trade, you can cancel quickly after. But the setup should update your stamps or allow you to do it manually once you press right on the Y menu. Once you have a set of stamps you can cycle through them to whatever you want. Most will want raids, so keep reading for more tips on that.
How to find more raids
Once you have a large number of stamps, you can browse through them all looking for something interesting, or you can take direct control. At the bottom of the Y menu is a search option. Select it and choose Max Raid Battles to filter the list down to only buffer raids. You can filter further, if you wish, but this should limit the buffer menu to only relevant ones. Scroll through them, press X to refresh if it's been a while, and you should see some nice raid options. Choose the one you like and join to fight the huge Pokemon.
And this is how to refresh the buffers to find more raids in Pokemon Sword and Shield.
