Once the buyer pays you, just go to the nearest JPJ or UTC. Bring the original vehicle certificate or more usually known as 'grant'. You can do the ownership change there. Alternatively, there are agents who bring the thumb print machine to you and do it straight from a laptop. For this, you don't even need to have the 'grant' present. Just IC will do. I sold my bike using both methods. Not difficult actually

Bike no need

Try posting on Mudah or FB marketplace or other selling platforms like Carousell etc. Before you do that, check the prices of similar aged bikes to yours then put a reasonable price. Remember, if you put almost same price as others, the buyers will normally have a hard time deciding. But if you have a lower price, they will be more interested to call you. You can price high if your bike is in tip top shape (which you must mention) and is at buy and ride condition. All the best.