How to get render bead on curved bench seat?

[bow2021]

hi  there, 

nearly finished building my garden fire pit bench. Want to start render next week but I did have a question about render bead. Obviously I’ve got curves on this and wondered if there are any products I can use like curved render bead suitable for outdoor rendering? Want to get clean lines (well as clean as I can get them) so really don’t want to just go free hand with no guide. 
thanks.

[Nic5]

Yeah it does. Thank you.