My best recommendation is to take your time on the prep stage. Get this wrong and it will all be for nothing. Also, when applying the adhesive, there is no such thing really as too much time taken. Rush it and it will be rubbish within a month.

If you can get hold of a smallpaint roller-type thing, even better. If you use your hands to push the material out, it will show the imprints from your finger. I normally use an old bank card and spread the material on using light pressure.