Using Heloc for BRRRR and finance

[Kam Nak]

I have read some posts here in the forum where people have used HELOC to buy a property cash out and then get a mortgage loan to paydown HELOC in 1-3 months after some renovations. One of my question here is when you use HELOC to buy out all cash property it would affect your credit score drastically. So now, when I go to the bank to get a home loan I would have a bad credit score to start with because of using good chunk of HELOC credit (either I would end up with a bad interest rate or my loan or not get a loan)

Am I missing something here ? what is the correct process to implement this strategy?