you can take part from mycelium on slide and add one drop from 1% NaOH or lactophenol solution .The slide test  under microscope .

But how can we make the slide to differentiate different strains of aspergillus?

like this..

Try to take the culture from the edge of the colony (were the number of conidiospores is less) on a tape and put slowly on lactophenol. Observe the lengh and the diameter of hyphae, the diameter of conidiospores, the shape of vesicle, the arrangement of phialides and spores. And compare for the Aspergillus species.