Time wise, at least for me, it is much quicker and more efficient than many types of Real Estate. 

All my rent increase communications to the tenants are done via a letter and an updated lease. 

Depends on how you are finding and communicating.  

I even use Skype and TeamViewer to communicate with clients so I'd highly recommend looking for one of the best with great references that interviews well with you.So look for someone you can connect with that works out for your situation.Feel free to ask here if you have questions

Sometimes that means communicating directly with the owners, it might mean a broker connects people without listing, and a whole host of other methods, most that occur by knowing people. 

However, it seems after lots of time and money, its making us LESS efficient. 

No matter how extensive the rehab, how good of a deal you negotiated on price, or how great your home inspector says the place is, your success depends on your PM managing tenants, collecting rent, keeping the place occupied, being smart with expenses, communicating well all the time, and communicating even better when there are issues.  

Below are reasons relationships fail, Marriage: Lack of communication, Lack of trust, Lack of commitment, and Unfaithfulness.

We are either a match or we are not.My time is very precious these days and I only work with serious buyers one on one who communicate in a timely manner and show financials.

It's the most time efficient method.