Hey John - Not sure if this tactic translates to RE perfectly, but I work in sales and one of the tactics I've found success in when trying to win someone over is to show them the financial pain of inaction and then visually graph the numbers on a chart/powerpoint/posterboard/etc right next to the outcome that I'm looking for a.k.a. doing business with me.
For example, if holding the property is costing the potential seller X, put that next to what they gain when they sell to you. If you know what they are going to do with the funds you're giving them (i.e. retirement, another investment, etc), you've got something even more compelling. You can show how them selling this headache to you for what you're asking for, gets them much closer to what their ultimate goal is than hanging onto it.
It's not a miracle formula, but even if he balks it will advance the conversation and show him you've taken his long term interests into consideration.
