We count on a number of techniques used for efficient result.
In this revised version of your sentence there is no ambiguity. The expression a number of is understood as a fixed-form quantifier, equivalent to “many” or ”several”. Consequently, this sentence will not be misunderstood in the particular way you fear.
However, it is still not a very good sentence, especially in a formal context, where language must be used with a maximum of precision.
First, some relatively minor points:
For efficient result is unidiomatic; we say either for an efficient result (article with singular) or for efficient results (no article with plural). It doesn’t matter much which you use.
A matter you have to be careful about is the common colloquial use of efficient to mean effective. Efficient means that your work involves no wasted effort; effective means that you arrive at the result you are seeking rather than at something else. We do not have sufficient context to judge which you mean.
There is some redundancy in the two expressions rely on and used for—both include the notion of a technique (or several techniques) being needed to achieve the desired result.
A number of (or several or many) is unnecessarily vague. You know how many techniques you have employed; why should you conceal this from your readers? It is simple courtesy to let your readers know exactly how many techniques they will have to deal with.
There are also two major points:
Efficient [or effective] result is a very dubious expression. Without more context it is impossible to know exactly what you should be saying; but I think it very unlikely that the result which you are aiming at is itself efficient [or effective]. What you probably mean is that you have developed a methodology which permits you arrive at the result in an efficient [or effective] manner.
The most serious problem is that it is not clear whether the multiple techniques you are talking about are individually efficient [or effective] in reaching the desired result or are efficient [or effective] only when all are used. I suspect (from your use of count on) that you mean the latter. You must let your readers know which you mean. Here are two contrasting examples:
Any of five different techniques may be used to achieve the result efficiently [or effectively].
Five different techniques are all required to to achieve the result efficiently [or effectively].
Note, by the way, that only the first two points above are matters of English usage. The others are equally valid in any language: they reflect the Adamantine Law of Written Language:
Anything which can be misunderstood will be.
