quite a few actually.
the most important things is to hide troops you don't want shot to bits, like the stegadon/s if he has many cannons.
to start off terradons, chameleons and the JSoD are all very effective at taking out war machines. be sure to have somwhere to scout chameleons and they will do their job, being harder to shoot at. these 2 units are also usefull post war machine killing. terradons can drop rocks and charge small units and chameleons can keep poisoning his gunline with little chance that they die. if you get close enough to his gunline with thme you can also move every turn so you force him to move his units to shoot at you, practically giving him -2 to hit them at all times. don't let your opponent place all the terrain elements so that it favors him. also the EotG bubble is quite nice when you can have a 5+ ward on anything he can shoot.
the next thing are the spells. both lore of heavens and lore of life are excellent. both uranons thunderbolt and forked lightning have infinite range and his war mahcnies are either on a hill or in plain sight, so your skinks should be able to blast them from the other table edge. 4+ ward save vs. shooting is also very nice from the lore of heavens and the comment of cassandora is the deadlyest spell against gun lines. they don't move and war machines are probably all stacked up somewhere as close as possbile. get a commet near a cluser of artilery or shooting troops and wach them fly.
the lore of life has 2 very usefull spells. the rain lore makes 1 unit get a permanent -1 pentaly to shooting wich can be used on his strongest shooters. it also makes war machines only fire after rolling a 4+ beforehand wich helps a lot. the other spell makes all units within 12" immune to shooting S4 or less. there aren't many rangead weapons with a S higher than 4 barring war machines so that should be up permanently if a slann is present. gift of life is also very nice if your stegadon/slann/characters get wounded by cannons or anything really, it just heals them up to full W. master of stone is deadly to anything on hills, where most of the shooting/artilery is.
basically, with all those spells he won't be able to dispell them all and his spells will be out 1st or 2nd turn, all tha while he has to worry about terradons and chameleons.