Most Bicycle units were still essentially Rifle units, Platoon-level radios were still present during the WWII era, and communication could be established over a short distance as a result, albeit awkwardly while on mount. Bicycle columns were often quite compact however, and word-of-mouth as well as traditional infantry hand signals would do the trick.

A wise commander would....detruck (for lack of a better word) early and conduct the move-to-contact on foot.

An example of a typical drill, in which orders are given verbally, from the US Army's short-lived Bicycle "Corps":

...the unit standard for crossing a nine-foot fence with their bicycles was twenty seconds. At the command of "Jump Fence" one soldier would lean his bicycle against the fence and use it to climb over.... (Tate, Page 31)

By 1944 Bicycle troops were no longer 'dedicated' tables of organization; a contrast from 1940 when armies of the Low Countries and even Germany themselves had specific tables of organization. As stated, they were simply being used as an expedient tool for the petrol-starved German army, and as a result we can reasonably conclude they probably lacked the specifically developed drills of Bicycle troops from the 1890s-1940.

By the beginning of 1944 German resources in both manpower and material were nearly exhausted. Petroleum was especially in short supply...

Horse drawn vehicles provided the majority of logisticaltransportation in the divisions. To give the combat units the required mobility to operate in a European environment, the Germans turned to the bicycle.

Each division received 1,522 bicycles. Seventy percent of the bicycles issued went to the infantry units in the division. A large portion of the Division’s engineer battalion were also mounted on bicycles. The rest of the bicycles were distributed throughout the division... (Ibid., Pages 65-66)

The article goes on, but no further mention of specific drill is used. Again, the conclusion that the expedient nature of why bicycles were employed to begin with (to add some level of tactical flexibility to a motor-starved army), coupled with the generally poor levels of cohesion and 'scratch' nature of VG and late-model Grenadier divisions: We must conclude that the Germans probably did not develop or re-visit any existing drills for Bicycle troops. The units barely had time to learn the basic rudiments of infantry combat and drill, let alone a drill for an antiquated unit-type.

This does not mean that there weren't specific hand signals or commands developed for Bicycle troops; simply that I doubt they were used very much past the year 1942 for the Germans in particular. Early war infantry reconnaissance was almost always conducted on Bicycles, however. These early, dedicated bicycle formations - referred to as "Radfahrtruppen" were mounted on dedicated military model bikes and drilled extensively on their tactical employment, maintenance and repair. While there appears to be a dearth of sources on the subject, we can logically presume that these units had developed a series of drills specific to the use of their bikes - including voice and hand commands, if we can infer anything from the earlier US Bicycle Corps example. Additional non-verbal communication would also come in the use of flare pistols - standard issue to Rad. squad leaders.

Sources:

Human Powered Vehicles in Support of Light Infantry Operations: Tate, Stephen T. Middle Tennesse State University.

World War II Combat Reconnaissance Tactics: Rottmann, Gordon L. Osprey Publishing.