I have to say I used a local professional to fit my screen, he happens to be a friend as well as a screen fitter so was encouraged into assisting or more to the point doing the job with me assisting.
He used a professional adhesive and used an air powered gun to apply a consistent bead of adhesive with the classic 20mm high inverted 'V' shape to ensure a complete seal, all the way round the glass seal.
He also use hard rubber spacers to ensure there was a minimum amount of sealant where the glass weight is applied to the frame.
Holding the glass to position it in the right place is also tricky without the vac pad holders/handles.
Its a one hit fit! there is no easy second chance.
Remember the face of the sealant between the dashboard and the inside of the window is a visible face and needs to be 'smart' and 'clean' as you cannot get in the gap to smear it flat and smooth and clean up afterwards as the gap is too small. The outside face can be bladed off for a clean finish as its accessible afterwards.
For what its worth...
My recommendation is
get it done professionally as you have to live with it for a long time afterwards if its wrong or a tatty finish.