If you are disciplined with credit cards and spending regularly on gas and fees you might head over to
https://www.reddit.com/r/churning/
I'm able to make between $500 and a $1000 a month (I do every card twice... one for me and one for the wife.)
If there is a good bonus bonus I'll buy pre paid gas or grocery gift cards... pay the credit card off out of savings... get the bonus and then use the gas cards for a month or three while the savings builds back up.
It's a little bit of effort and you need some cash on had as well as a spreadsheet so you know exactly which cards are opened when... what the fees are and when to close them if there is one and it's a terrible idea if you don't have the cash and don't pay the cards off immediately.
As for my credit score. I started at about 780. After 2 years of 'churning' and dozens of credit cards I've noticed it will run my score up and down a bit. As low as 700 at one point 'too many new accounts opened' and then in a momnth or so it will drift back up to 760 or so.