Increase prices for your new customers and raise old customers prices when you have enough work not to worry about losing them. As you said it`s a numbers game and when they`re right increase the prices accordingly. Make sure that all new work is priced correctly.
Being trad you`ll be a lot slower than wfp but you can still earn as much as me. Don`t let anyone tell you are charging too much or too little, it`s your business. Some customers will pay more than others. I`ve got some from the start who are stupidly under priced but they`ve been loyal and reliable so I keep them at that price because I`m happy with that but I wouldn`t charge the same for a new customer.