You're just going to have to go for it. I trained my two boys when they were two to two and a half. Wearing cloth training pants worked well with my first boy... he didn't like being wet. This didn't work with my second, so I just let him go naked at first. He was harder to train.
I decided to lay out a big plastic sheeting type thing in most of the living room and just sort of set up camp there. I made sure I didn't have any plans for the week and decided it'd be my potty training week... no looking back.
I did end up having to go out a few times, so I either put plastic panties on him or cut up a garbage bag and laid it over the carseat.
You'll need a lot of patience, but just try to keep him in your sight and when you catch him in the act of peeing or pooping, rush him to the potty and hopefully some of it will end up there. Keep potty chairs at different spots throughout the house, so they're always close by and available. If he doesn't warn you or try to go to the potty on his own, then give him a few practice drills.
After cleaning up the mess. Tell him, "Remember what you do when you need to go pee or poopie? We hurry to the potty. Let's practice...." Take him to where he had his last accident and say something like, "Uh-oh, what do you do when you have to pee or poop? We hurry to the potty." Then walk him quickly to the potty. "Pull down your undies, sit on the potty and then we pee(poop)." Direct him into each of these actions when you're saying the words. Then go through a practice drill a few more times.
This is how I did it with 2 year olds... I think it'll probably be easier for yours to catch on, because he's older. It can be frustrating at times, just remain patient and know that it'll get better and better each day and he'll be trained before you know it. Also expect times when they'll be doing real well and you'll think they're trained and then they revert back. Just keep at it and they get it... it can be like that saying sometimes.."3 steps forward, 2 steps back" The key is not to give up though.
I hope some of what I did can give you some ideas. Good luck!