Craigslist is what I used to build my buyers list, but I wasn’t sure if it was an outdated lead generation source.

You can't just make a blanket statement and say LTR's are safer in every market, and STR's will generate more revenue that a LTR in every market, etc..   

You should always be doing lead generation as a wholesaler.

However, you have very little risk now compared with what you'd have to take on to do so.If you are willing to let your timeframe slip, the properties you do own will likely appreciate further and continue to generate more cash flow.

Also, was this a rental in the past that generated foreign tax credits?

There is no need to generate some list, and hope that it is a good one.

For example a i have an investor client who we searched for the right property for about 9 months but once we did find it now he is generating $2,000 positive cash flow each month which is amazing. 

The property generates $2600/month right now, and conservatively will generate at least $4000/month when full rented. 

Also I really want to have unique pin codes automatically generated and sent to guests.

Nothing else.It is my experience that NOT A SINGLE PERSON in such meetings has a clue how to generate such leads hence these meetings are a waste of time.