The evil one's minion are in a hierarchy below him and their abilities decrease at the lower levels. So that changing staffs into snakes requires one of the few higher level demons or we'd see a lot more of that kind of thing. I suspect that the lowest level of demon ranking interact emotionally in their attacks, rather than verbally. When we are being demonized, they use the same voice that we talk to ourselves in. When You think, how can I think something like that at a time like this," its probably a demon who'll then accuse you of being unsaved for thinking something like that. As far as a cure, I have a couple of suggestions. As you mentioned see Jam 4:7,8 "Submit yourselves therefore to God, resist the devil, and he will flee from you. Draw neigh to God and he will draw nigh to you, cleanse your hands, ye sinners; purify your hearts, ye double minded." Turn to the Lord in repentance which is how we submit to the Lord. Resist the evil one and his minion. And keep resisting. Jesus gave the church authority over all the power of the enemy. Their gates are a defensive weapon and will not prevail against us. With our faith in God's word we are able to order them away. Faith grows with use and scripture and if unable to resist now, keep resisting because submitting yourself to God and drawing near to the Lord who is found in the scriptures by the Spirit's ministry, are the very things we do to have our faith to grow.
First; Ps 22:3 tells us the Lord inhabits our praises. The evil one and his minion know in a way that we never will while absent from the Lord in these bodies of flesh, what its like to have the Lord inhabit our praises and the glory of the Lord's presence will drive them way in torment. Prayer and fasting go a long way in successfully dealing with the enemies strongholds.
Second; according to 1 Jn 4:1-3 we are to try the spirits whether they are of God. No spirit can say that Jesus Christ has come in the flesh, but by the Spirit of God. So just ask the demons that are attacking you, has Jesus Christ come in the flesh, and you may very well find that they slowly one by one depart with a gradual lessening of your torment. Just ask them over and over, "Has Jesus Christ come in the flesh? Well, has he? What, I can't hear you?"
I've come up with this reason for why the Lord would allow demons to exist along beside us at all: The evil one and his minion have no forgiveness; no second chance. Like Adam they were made perfect, but unlike Adam, they didn't have any outside force working from inside to do evil. Its only fair that we get a chance for forgiveness because we've had evil attacking us from the inside where they did not.