Our son was a 4-2-4 and signed in the early signing period with a D1. The D1 brought him in to start next year to fill a need. You or your son have to be proactive in putting out the word - contacting possible choices. There were JC showcases in the Fall. Key in the process is your JC coach. Have your son talk to him about where he thinks he can play. I assume you can find out what your program's track record is in getting kids to the next level. But college applications should already have been in, so get going.
As to how they find you, college scouts were at all the Fall scrimmages, and numerous pro scouts at our games too. The baseball community is a small one, and if your son performs, everyone will know. BUT - since nothing has happened yet, you need your son to send out letters, and follow it up with emails showing interest in the programs he thinks need a player like him. If you are not in a nationally ranked JC program, you have to work harder.
Last year, the top four pitchers signed in the Fall (four drafted and 2 signed), and the graduating position players and relief pitchers all signed in the Spring AFTER their JC season. That is because the coaches have a better idea of what they needed after the season ends and the draft takes place. Those players signing in the Spring went everywhere from the D1, D2, and NAIA levels. Obviously the kids signing in the early signing period got more scholarship money. My son's friends at other schools with less influential coaches had to scramble and go to pro showcases - signing right before school began in the Fall. I know it is nerve wracking to wait, but that is part of the process.