A second type of complex noun consists of a verb followed by a suffix meaning one who does or thing which does. The English suffix -er (as in builder "one who builds'' or toaster "thing which toasts'') is a rough equivalent. In Klingon, the suffix is -wI'. It occurs, for example, in baHwI' gunner, which consists of the verb baH fire (a torpedo) plus -wI' one who does. Thus, baHwI' is literally "one who fires [a torpedo].'' Similarly, So'wI' cloaking device comes from the verb So' cloak plus -wI' thing which does. So'wI' is a "thing which cloaks.''
A noun formed by adding -wI' to a verb is a regular noun, so it may be used along with another noun to form a compound noun. For example, tIjwI'ghom boarding party comes from tIjwI' boarder plus ghom group; and tIjwI' comes from tIj board plus -wI'.
In reference to inanimate objects, this suffix means "thing which does" (joqwI' thing which flutters) or "thing which is used for" (nanwI' thing which is used to gouge).
In reference to animate beings, this suffix means "one who does" (baHwI' one who fires) or "one who is" (pujwI' one who is weak).
Regarding -lu'wI' —
For poetry (and maybe other literary forms), this sort of thing may occur from time to time, but it's not considered "normal" grammar. This is because the meaning of -lu'wI' (from a Klingon point of view) is odd (but therefore occasionally appropriate for poetry and such).
Leaving -lu' aside for a while...
-wI' is defined as "one who is, one who does, thing which is, thing which does." In all cases, the subject of the verb (to which -wI' is attached) is the doer or the "be-er," the one who performs the action (if it's that kind of verb) or carries or exhibits the characteristic (if it's that other kind of verb). The noun formed by adding -wI' is equivalent to the subject of the verb to which -wI' is attached (as far as meaning goes — not getting into fine points of grammatical description).
yItwI' walker (the subject of yIt is the yItwI')
qIpwI' hitter (the subject of qIp is the qIpwI')
wochwI' tall one (the subject of woch is the wochwI')
When -lu' enters the picture, things change. The subject of a verb with -lu' is "unknown, indefinite, and/or general." Thus, qIplu' is "someone/something hits (someone or something)" or, conventionally but not really literally, "(someone/something) is hit."
So qIplu'wI' would mean something like "indefinite hitter" or "unknown hitter" or "essence of hitter" or some such (if it means anything at all). It doesn't refer to the person (or thing) being hit because a -wI' noun is the perpetrator or instigator of an action (or carrier of a trait), not someone (or something) affected by an action.