Hi Jaffa, and welcome from me, too.
In my experience, you don't have to encourage them, they just moult anyway!
Moulting is due to hormonal changes at the end of the laying season, as you say in late summer when the days are becoming shorter and there's less daylight to stimulate lay. The only way to keep older hens laying is to keep them under the stimulus of electric light, as they would be in commercial conditions, not free range as yours are.
Pullets that are hatched in Spring will usually come into lay between August and October, depending on breed and how early they were hatched, and they will continue in lay throughout the first winter and usually moult at the end of the following summer. So if you want hens in lay between late autumn and early spring, you could replenish your flock by getting POL hybrids between July and October, to lay whilst the older ones are moulting and having a well-earned rest. At this time of year, integration of newbies is much easier as well, as the older birds are less aggressive when not in lay.
How many hens have you got, and how old are they? Breed is also a factor in length of laying life, with purebreds tending to lay fewer eggs over more years, whereas some commercial-type hybrids will lay almost daily for 2 years, including in winter, and then slow down or stop much sooner because all their egg cells will have been used up - the 'henopause.'