Apply at the suggested spreading rate, ideally using a good fertiliser spreader - try to spread on an overcast day or in the evening. If it is spread without a spreader there is a risk of scorch
Try and fertilise when rain is forecast. If it is dry, water in after fertiliser is spread
Grass blade burn prevention - please bear in mind it is really important to water off the fertiliser from the grass blades as the fertiliser will burn and damage the existing grass. Our top time saving tip is to fertilise on a day when you are expecting a good amount of rain so it does the job for you otherwise just water it off yourself using a hose/sprinkler system.
Most slow release fertilisers will last for 12-16 weeks and most quick release/liquid fertilisers are 4-6 weeks.