with ojama farm you want a ojama knight or king turn one or two, that way marik cant use his masked beast, you just need to wait for the last turn, since he cant beat your knight and cant golem with one monster on your side.
No because I imagine he will have Masked Beast Des Gardius which is stronger than blue eyes and he might have lava golem which he can summon by tributing 2 of your monsters. Ojama Lock works best trust me, I farmed him with it