How to exploit calling stations pre-flop?

So today I had 3-4 players on my table that refused to miss out on the flop with any 2 cards.

I got dealt KK UTG. I open to $25(at 1/2), and I still get 3 callers.

Does that mean $25 wasn't enough and I should try more next time?

Is this the correct exploit here? Start opening insane amounts like $40 if there are players that refuse to fold pre?

I see otherwise solid regs open to the standard $10 and get 5 callers. Like whats the point?