MLU Controller experienced a loss of separation event during CENRAP operations; noting the need for training in the use of this rarely used procedure.

Narrative

I was informed that my manager is investigating 3 operational errors involving my session on RADAR. This is one of them; a Citation was heading 320 off of Runway 4; climbing to 12;000; the aircraft came onto my screen from the (more than 40 miles away) west descending to 13;000. When the Citation was inside 2 1/2 miles from Shreveport's airspace boundary; I descended it to 5;000. I told the Citation; (heading 320); to report leaving 5000' so that I would have an idea of when I should see him in CENRAP (Center Radar ARTS Presentation). I then turned the Citation left to a 270 heading. Right after; I saw what appeared to be his beacon code and altitude so I told him to 'IDENT' and RADAR identified him. The Citation was cleared direct SABAR; the OM 4 miles south of the MLU airport. The aircraft were more than 20 miles apart and I considered aircraft performance in my decision to turn the Citation to the west. Recommendation; MLU does not go 'CENRAP' often enough to keep everyone current on NON-RADAR rules and separation. No one seems to have a clear idea of how to apply NON-RADAR rules here other than 'one in; one out' of the airspace. This is not practical when the airspace is up to 12;000' and has a 30-40 mile radius. I made it known before I took position that I needed to review the NON-RADAR rules and I was told; 'oh; the separation just increases from 3 to 5 miles and Local has to call RADAR for IFR release'. I should know the NON-RADAR rules. But I admit that; rarely working NON-RADAR; I am not as proficient as I would like to be.