If you need to fill gaps and smooth areas around a door, ARDEX A 46 Multi-Purpose Repair Mortar can help get the job done fast. There's no priming required, it can be used at depths of up to 50mm, and sets within 30 minutes with a shrink and crack-free finish. It's also easy to smooth too. Just let it start to set for 10-15 minutes and apply a damp sponge to get the finish you need. From there it's printable in 4 hours.