@Paul Bloomfield
Creativity will be the name of the game here. The exact strategy you choose really depends on the exact $$$ numbers you are working with, the type of tenant you have in place, and the property itself.
Based on what you have shared so far, I would consider the following strategies:
(1) Offer the tenant a generous early move-out bonus, if they move out in 60 days. The exact amount is dependent on the type of your tenant you have. So many people live month to month in our economy that you may be surprised what 2 or 3 months worth of rent will do towards motivation. Other tenants may be a bit more wily and propose more.
(2) A variation on (1), offer them a "commission" to help you "sell" the property. Some tenants knowingly sabotage a sale by making buyer walk-throughs very uncomfortable, or worse making it nearly impossible to schedule a buyer-visit. To combat this, you can offer them a commission incentive to actively participate in the sale and tell buyers how wonderful a property it is. I do this on a sliding scale, the maximum if the sale goes through in the first 45 days, and then tapering off after that. We are not talking (6%) realtor commission here, just a couple of months of rent. Option 2 is not as favorable as option 1, and again it depends on the type of tenant.
(3) Find a buyer off-market who will be willing to wait the 6 months for the lease expiration. These are hard to locate, but I have been successful with this strategy, finding a buyer once who was willing to wait 9 months after purchasing the property for the lease to expire because she really wanted it. The viability of this option depends on the desirability of the property.
Hope you find this info useful. If you want to discuss the specifics on the above, let me know, I'm happy to help.