Dennis, at age 49 when the war started, Greenberry Manuel would have been too old for service in the Provisional Army of the Confederate States. Although there were some older men who volunteered in various Arkansas regiments, most of them were ordered to be discharged in the summer of 1862, when the Conscript Act came into effect (it initially set an upper age limit of 35, modified upwards at various times during the war). He may have served in a home guard company, but records of these units are very scarce.
The only Manuel from Searcy County I can find any record of among Arkansas soldiers is John F. Manuel, born c1837 in Wayne County, Tennessee. He served in the 45th Arkansas Militia and the 32nd Arkansas Infantry, then deserted and joined the 3rd (U.S.) Arkansas Cavalry.