My KTT box is now primed (this word suddenly struck me as correct, right?
Yes.
- A primer will prime (future tense).
- A primer is priming (present tense).
- A primer has primed (past tense).
That general rule applies to many verbs.
So, the box is primed because the application of the primer has completed its job.
Just to make it more interesting, English has 12 tenses, there being 4 each for present, future, and past. And then they can be broken down into first, second, and third person aaaagh.... However, in many cases the same word is used, the difference being some of the words surrounding it.
Fortunately though, getting the grammar wrong rarely changes the meaning. Unlike Chinese (for example) there are so many extra words that they act almost like error correction
English has plenty of exceptions (and I'm sure you're aware of some). In this particular case, some words don't follow the rules (there is no "runed" to indicate the past tense of run, the word is ran, likewise there is no "readed" for the past tense of read, the word is read -- and the pronunciation is different).
In general the mark of a person who has learnt English as a second language (for example, Americans) is that they often make certain styles of grammatical errors which are obvious to a native English speaker, and which can often reflect their native language.
(I was joking about Americans)
You have commented a few times that you are not a native English speaker, yet you make very few errors which suggest this. Either your native language has a structure similar to English, or you have managed to learn the grammatical rules of English extremely well.
I would point out that English speakers (if about to comment about a person not involved in the conversation having just completed an oral hygene regeme) would never consider that they need to use the third person past continuous tense, nor concern themselves with the lack of a singular form, they would just say "they brushed their teeth".
Having had a go at learning Mandarin, I know that following the rules and missing the exceptions can result in you calling your teacher a rat. Another thing is changing the emphasis on a word can change it from horse, to road, to mother, to the equivalent of a question mark.
Anyway, with my Mandarin vocabulary of about 5 words that I can't get straight, all I can do is compliment people who can write English as a second language and do so as competently as me.