In the old testament the Holy spirit was not indwelling but often came upon prophets and selected individuals. The Prophets even though couldn’t trigger the presence of the Holy Spirit but could put themselves in a position to be inspired by the Spirit. In the old testament, the people of God couldn’t be guaranteed of the presence of God always.
The Holy spirit was responsible for the inspiration of the Prophets in the writing of the scriptures and this is what false prophets never had. These inspiration was not forced or triggered by the Prophets. Prophets and men such as Daniel, Ezekiel, Othniel, Gideon, Moses etc Just to name a few were able to carry out great and mighty feats for God through the sometimes overwhelming inspiration of the Holy spirit.