What day are you in? If it is early, than the only way is use your on artillery. Planes can also be a option. But be aware that artillery has a 1.0 defend point. Does that help you? But level 1 bomber when attacking, attacks at 1.0 but artillery defends at 1.0 so if you are trying to completely destroy it by plane, you must sacrifice your plane.

Artillery are fragile. You need to get out there and attack them. Generally a fast unit helps. Circle around them with an armored car or two sometimes works if they just have a few.

Many players will have a blocking force between you and their artillery, so that makes it harder. Planes work well if they have their arty separated. Then if they group it back up with their blocking force send a large group of whatever you have, tanks or regular infantry, and try to catch them.

Early game? More arty. Tac bombers are also good as an anti-arty measure (especially if they're upgraded) but if that arty regiment happens to have some AA cover, your bombers will lose efficiency.

mass tac bombers and mass rockets is what I use

Most often I use tac bombers, light tanks, and/or infantry- the last two when artillery is paired with AA. If they have a blocking force in between, it all depends with what that force is made up ...