Hi, newbee "mason" here. I have castable high temp mortar that I tried to use to butter between the bricks on the arch entrance and the mortar slipped off. Then when filling the wedge spaces between bricks, gravity wreaked havic. Seemed like the mix was to dry on flat surface and to wet when applied vertically. I felt like Lucy trying to rebuild Ricky's BBQ! Thanks in advace for any advise. PS- I did wet the surfaces but ever so slight.