Cut out the easy mistakes - there is no hurry to attack his service if it is a good one - you know he is not likely to be attacking your return. Concentrate on making good safe returns while picking off any bad services. If you seem to be attacking well then try to attack a few more serves, if you are missing your attacks be content to push the ball back and wait for a better opportunity to open up.
Your opponent is stronger with his backhand defense, so most attacks should be placed to the forehand side, which also has the benefit of avoiding the long pimples which you are not so good against. Occasional attacks to the backhand must still be made in order to keep him honest though, and to stop him covering too much of the table with his backhand chop. As he edges further to his forehand, hit wide to his backhand side to bring him back over to his left and keep that forehand side available for you to attack.
Going to his crossover point is a good idea too, but remember that it isn't his right hip - it's a foot and a half further over to the right!
Opening the Attack - First Attacking Shot
The main thing here to remember is to take your time. Your opponent does not have a strong attack and is not going to be putting you under pressure - so relax and wait for the right ball to start your attacking sequence. If he returns your service well, push the ball back to his forehand smooth rubber and get ready to attack the next ball. You could also use a slow safe loop if you prefer. The main thing is that you have plenty of time to choose the best ball to attack - so stop going for the 50/50 ball - you can afford to wait for the 90/10 ball instead.
If you are having problems playing against his pimples that day, wait until he pushes the ball with the smooth rubber before attacking. Try to get at his forehand and the smooth rubber. If he covers more of the table with the pimples on the backhand while pushing, go out wide to the backhand to move him to his left, then go back to the forehand. If he twiddles and hits the forehand with the long pimples instead, simply continue to push the ball to both the left and right sides of the table until he eventually pushes one with the smooth - sooner or later he will, and you can afford to wait until he does.
Once you have opened your attack, watch his return carefully. Remember that he is not so great at spinning his forehand chop, so be looking for the float but be aware that it might have some spin. The better your attack the more likely it is that he will have to resort to floating the ball back.
Follow Up After the First Attacking Shot
If you are confident that you have got a correct read of the spin on the ball and it's not been returned too tightly, attack it again. Your choices here will depend on the quality of the return and your opponent's position. The worse the return the harder you can attack it - setup balls should be put away, high deep returns should be attacked with controlled power, etc.
The direction of your attack should generally be to the forehand to get another return from his smooth rubber - save the backhand side for kills as you don't want to give him the opportunity to load up the spin with his long pimples, since you may find that difficult to attack again. It's just a matter of knowing that you don't like the long pimple chops and avoiding giving your opponent the chance to use them easily.
Since your opponent twiddles occasionally, he'll probably turn the bat over every so often on the forehand to chop with the long pimples. This ball will probably be loaded with backspin in comparison to his normal forehand chops, so I'd recommend pushing the ball back and waiting for another opportunity to attack, since your read of spin is only average. Remember, you have plenty of time, you can afford to wait and try again - avoid giving him a cheap point through your misread of the spin.
Tight returns should be either attacked with care or pushed back to wait for another opportunity to attack. Returns that you are unsure of the spin should either be safely looped to the middle of the table with enough arc to give you plenty of margin for error, or pushed back to the middle-backhand side of the table, since your opponent will only be attacking set up balls and will find it difficult to attack from his backhand side, since he lacks a backhand attack.
