Yes, in fact, they make up the bulk of these boosters
Bristly Bill does a great job circumventing one of the issues with counter doublers that need another source to add counters in the first place
2024-03-08 If a player or permanent has more than one kind of counter on it, and you choose for it to get additional counters, it must get one of each kind of counter it already has
Glimmer Seeker (DSK-014) - Duskmourn: House of Horror Glimmer Seeker (DSK-014) - Duskmourn: House of Horror Wizards of the Coast This item is like new, pulled from a sealed pack
The other use I can think of is that Karn's card draw isn't worded as "drawing," so if you're a horrible person and want to lose your friends, you can pair Karn with mean cards like Possessed Portal or Omen Machine to lock them out of the game while you keep your hand nice and full
(Though, if you have enough mana fixing, you could maybe splash for a third color if you wanted.) But if you want to shop around to other colors (what's more Dimir than having a Dimir deck box when you're actually playing Selesnya, I suppose?), things that may draw you into specific colors are: A really strong rare you're excited about
