Then i had to resolve multiple lockouts this year, wasting 4 hours commute (I couldn’t say go get a locksmith)  What solutions have worked for you?  

Minus a dump fee for the fridge "I left behind" and a rekeying fee because they claimed they never got the keys back.

Here whether the person residing in the property is a former home owner or a renter makes no difference.They become a tenant at sufferance at that point whoever they are and you must evict if they will not leave on their own.Here in Georgia if the property looks vacant and no more than 500 of personal property is inside you can re-key and fore go the eviction process at your own discretion.Cash for keys can be good but a word of caution.You don't want them to agree to cash for keys and then renig on the deal and make you evict them.You will have lost even more time.Instead you go ahead and file eviction and then get an agreement for cash for keys.This way they know if they renig on cash for keys you have the eviction in process to get them out.Ask for the property to be left in "broom swept condition" and free of junk.They don't get the cash until everyone is out of the building and it is clean.Make sure and change ALL exterior door locks and not just the front.

You would simply deal with re-keying (and charging for re-keying, if applicable).If they gave you written notice of their intent to vacate (30 day notice or whatever), then verbally told you that they were done vacating but didn't give back the keys, you could probably change the locks and there wouldn't be an issue (especially if they didn't leave anything behind).

Then you just let the post office know and they will rekey it for free.

My lease states "Landlord may deduct from the Security Deposit, Any unpaid rents, court fees, locksmith fee if keys not returned, utility bills, late charges, court costs, damages due to breach of this agreement, and damages to the premises by Tenant, their family, agents, employees, or social guests in excess of ordinary wear and tear."

This can be done without rekeying the door, and having to distribute keys.  

It will be nice to buy something without having to call a locksmith to go in and see what I really bought.If I don't have any luck with my broker friend (I trained her), I'll leave a message here.Thanks for the input, I really appreciate it.Mirko

They re-keyed the locks, secured the windows, and padlocked the house.

I called a locksmith and changed  the locks.