Here's how I do it and it really nothing scientific at all, more stubbornness on my part I guess.
The only bank stock I own is JPM. In February, the low was around $50, and when Dimon bought I think $25M worth of stock around $54 and that's when it took off. So I'm not buying anymore JPM above $54. There is strong demand at $54. The other side of the coin is that if Dimon bought at $54 in February, if he doesn't buy again when it gets low, this stock could tank. I'll worry about that then but I won't buy JPM above $54.
Also with financials, the market was pricing in higher rates. That is obviously not going to happen this year so that hurts banks. I think JPM and other financials still have room to drop.
A major world currency dropped 10% overnight, we're not going back to normal anytime soon.