Hi Johnny, yes it can actually be very difficult playing against an experienced player using a sandpaper type bat. The sandpaper produces basically no spin at all so it’s a bit different to long pimples which can have the effect of almost reversing the spin.
With sandpaper it can float back and stay quite low but it’s never got a lot of spin. Pushing with backspin against this is good because it’s hard to attack with a lot of power with sandpaper when the ball is low, then you’ll be looking for the ball that sits up a bit higher to try and attack into the body. This way its harder for him to keep retrieving the ball back.
Being patient is key as well and not rushing to win the points, sometimes good defence and blocking like you said is key to keep you in the points.
Lastly if you can get him wide out at an angle early in the point this could force him back away from the table where it can be harder to play with that type of bat.
Hope this helps and that you can start beating him more regularly!