To make a neat bead of sealant with no skill needed, buy some "corner tape"
This is just two strips of masking tape, on a backing to space them, that when applied gives you two strips of masking tape either side of where you want the bead of sealant, nice and evenly spaced. Apply sealant, wipe to get a nice bead, and remove masking tape while still wet. Once perfect looking bead of sealant.