Ok last post for now.
When trying to inform catholics or the unsaved of the truth in the bible in the presenceof a catholic we have a huge up hill battle. The reformation is only 500 years old. Both the eastern Orthodox and the catholic church have a huge head start in shoring up their defenses againsts counter-claims.
When dealing with a confirmed catholic it is important to discuss each docturine/dogma individually without allowing the topic to be derailed. If you talk about the Assumption of Mary (Jesus taking Mary bodily to heaven) one thing you will point out is there is not scriptural evidence for that. They well likely attack with their position on Sola Scriptura. If you let that happen you will lose. Why? because your no longer on topic. Simple acknowledge that your commenting on the lack of scripture and that the catholic church claimes to have cannonized the bible at the council of Carthage in the late 300's, long after this event was supposed to have taken place.
Next point out what scripture supports Jesus not Assuming Mary Like the fact that Jesus, on the cross, made the Apostle John her son to care for her effectively removing Himself from the role of eldest son and substituting John is His place.
These of course are just ideas and not a formula for combating catholic tradition. Again the key is to keep it on topic and not to try to deal with multiple traditions at once. Also, just like reading your bible will help you understand what God wants from and for us. Knowing the history of the church and researching credible sourses will help combat bad traditions and support those that are in keeping with what the bible teaches.