I too have this problem at times, although it can be reassuring to new landlords that you cannot keep up with supply, it does not help revenue

I try a number of methods, but it does seem to take a while to get established.  The only way i have successfully pulled in new landlords who would have done it themselves, is to tactfully show the costs of DIY and then what it does cost with an agent.

I am worth my weight in gold, the same cannot be said for agents i have used in the past, so if some landlords have bad experiences with agents it is understandable.

The biggest benefit you can offer is no let no fee... then set realistic fees.