LBO Model - Which method works best?

Hey guys!
So I've been preparing for my M&A interviews lately and I have a doubt regarding the LBO Model.
Basicly, I have been seeing 2 different models:

1) Entry & Exit multiples are assumed and a target IRR is set but you know nothing yet about purchase price & equity use; you work out your financial statements, determine the debt schedule; get the final EV at exit period with your exit multiple; then take off debt remaining and divide by (1+IRR)^period to get the NPV of equity value, divide this by fully diluted shares outstanding and then determine if you invest or not based on the premium you're paying.

2) You do have purchase price & some form of equity use but know nothing about the IRR first; you work out your financial statement and your debt schedule; you get your exit value just as in method 1) but this time you take off the reamining debt and determine the IRR & the MoM by inputting your equity use and your exit value.

My question is the following: are both methods correct? And if they are, which one is superior?

Thanks :)