The route takes place mostly on the RAVeL of the line 87 and the Dendre which are part of the Wallonia Picardy waymarked cycle network and the cycle network of the Province of East Flanders, so all you need to do is follow the markings throughout this stage.
From Renaix/Ronse, on line 87, follow numbers 91 and 90 of the Province of East Flanders network, then the signs of the EV5 Ellezelles to Flobecq, or numbers 79, 82, 87, 8, 11 and 14 of the Wallonia Picardy bicycle network.
Warning: the RAVeL on line 87 between Flobecq and Lessines is under development and to reach Lessines, you have two options:
Either take the regional road N57, Chaussée de Renaix (which has a cycle track, but fast traffic);
Or follow the local roads and paths of the Wallonia Picardy waymarked cycle network for about 13.5 km. The numbers of the waymarks to follow from waymark 14 onward are 23, 13, 22, 3, 7, 6, 5, 21, 18, 28, 37, 44 and 45, at which point you will reach the RAVeL of Dendre in the centre of Lessines. Between waymarks 28 and 37, the road is unpaved for about 700 m. From Lessines, at waymark 45, all you need to do is follow the RAVeL of the Dendre. The course of the river and waymarks 30, 32 and 28 of the Wallonia Picardy network by bicycle route, then 83 and 81 of the Province of East Flanders bike network, guide you to the centre of Grammont/Geraardsbergen.