I keep thinking of putting together a quick anti-witness presentation for if they come to my door. Just state that the three beliefs that you heard of were 144,000, the great crowd on Earth, and Jesus returning in 1914, ask them to explain it. First the 144,000. When they show you the scripture say
"so the 144,000 are made of Israelites?"
When they explain that when they talk about Israelites being the 144,000 ask them how everything in that scripture is symbollic except for that number. Just point out everything "so this is symbollic, this is also symbollic, this too is symbollic, but this is literal?"
Regarding the Great Crowd say you heard something about a great crowd that has an Earthly hope, ask them to show you the scripture. Which they will, ask them how they know the great crowd is on Earth, which is usually something about them being "before the throne" and therefore and Earthly hope. Then ask if the 24 elders and the 4 creatures are also on Earth. They should say no, which you show them in Revelation 7:11 that they were also "before the throne".
Finally ask them about 1914 and how that is calculated. If they know their stuff they should at least mention something about 607 C.E. and the destruction of Jerusalem, then just tell them. "That is all well and good except for the little problem that Jerusalem wasn't destroyed in 607 C.E." Tell them about the actual date of 586/587 being the destruction date.
Close by asking them to read 2 scriptures:
2 Thessalonians 2 :1
When our Lord Jesus returns, we will be gathered up to meet him. So I ask you, my friends, not to be easily upset or disturbed by people who claim that the Lord has already come. They may say that they heard this directly from the Holy Spirit, or from someone else, or even that they read it in one of our letters.
Luke 21:8
Take heed that you are not led astray; for many will come in my name, saying, `I am he!' and, `The time is at hand!' Do not go after them.
Finish with "I'm sorry here, but I'm going to have to defer to Jesus here and not go after you"
And always keep handy the following scripture if "new light" comes up:
2 Timothy 3: 7
always learning and yet never able to come to an accurate knowledge of truth.
One would hope this would disprove three core beliefs in the matter of minutes and hopefully too quickly for them to come up with a rebuttal. Hopefully putting some doubts in their mind. Anyone who is a current witness think this would work?