I apologise for the delay in my reply. If you wanted to know how to paint skirting boards without getting paint on your floor or wall I would highly suggest using the UNi-PRO 600mm Steel Edged Trim Guide.
You simply place the straight edge in between the floor, carpet or wall and the skirting board and paint the section. Keep a rag with you and every time you move to a new section wipe the straight edge off from the residual paint. This product is super handy when you have plush carpet as it allows you to push it down and out of the way.
Alternatively, if you don't have carpet you can use masking tape on the adjacent surfaces to the skirting board protecting them.
Please let me know if you need further advice or had any questions.