ProGRP training courses are available to become a registered installer. GRP roofing systems installed by registered installers receive 25 years guarantee. Become a certified Cromar ProGRP tradesman with the full day GRP training course; you will learn the ins and outs of every tool required for the job, how to prepare and then lay your decking boards, the process of installing various trims, applying the fibreglass mats and resin and finally finishing with a topcoat. Youand#039;ll also learn various tips and tricks to make the application faster and tailor it to your own preferences.