If he were my father, and I was tasked with the application of knowledge from here and elsewhere to aid in his repair, the first thing I would do is tell him to stop applying for credit. Repair then rebuild. If he has no CCs, then he'd definitely benefit with one, but if he's in a financial bind to where paying a car payment is tough or paying medical bills is a challenge, then a CC or any other form of credit is the last thing I'd ever recommend. It doesn't make sense to start repair, then rebuilding, if there's a prospensity for lates being added.
The first thing I'd do is make sure he's 100% on time. If there's a budget shortfall each month, the first thing I'd advise is to cut expenses and increase income, all the while selling off assets to have spare cash for emergency funds, savings, and extra funds to pay off bad debt so as to aid the repair process. Once his ducks are in a row, then I'd tell him to start repair. The last thing he'd ever want is a CC in a negative shortfall. The first thing people do is use CCs as a crutch and the cycle continues of bad credit.
For repair, the BK will continue to drag scores, but there's not too much he can do. I believe BK7 reports for 10 years. I have seen some examples of scores into the 700s with a BK7 reporting, so it isn't the end of the world.
For the medical, once he has the savings in place, then I'd tell him to send DV letters to each of the medical CAs. If they verified and he agreed, then I'd tell him to send a PFD letter. If they agree in writing, then tell him to pay it off and they'll delete and that'll help in a big, big way.
Tell him to pay the car on time no matter what. Per FICO scoring, it's viewed as an installment vs. a car loan or personal loan so don't worry about the description. It's up to the lender to report to none, one, two, or all 3. They don't have to report to Experian. He can ask them to but there's no requirement.
PEr offers, the collections are holding him back. There's a chance his Experian FICO is in the 500s. IME, EX FICO weighed baddies pretty heavily. Even when my scores were approaching 700, I wasn't getting any offers. IMO, it's too early for that anyway.
I would advise him that once his finances are stable, and repair is wrapping up, then I'd suggest to him to get a secured CC from somewhere. Getting that first CC is tough and to avoid added inquiries, a secured CC is the way to go. The limit doesn't matter per FICO, but higher limits begat higher limits. After that reports for several months, then it'll be easier to add a 2nd or a 3rd.
Starting Score: 5/2012 TU 595, EQ 565, EX fako 547