I’m no expert in cookie decorating but thought I could share what I have read up, trial and tested. Basically I used 3 tips for cookie decorating, being Wilton Tip 2 the most commonly used.
Wilton Tip 1 – used for writing, very fine tip
Wilton Tip 2 – used for outlining
Wilton Tip 3 – used for flooding or outlining
A coupler will come in handy when you need to change tips using the same icing color and need not change the whole piping bag.
It will depend on the number of icing color you used, I usually use 1 basic white color and 2 other colors – pink, green for outlining. In this case, I will need 3 x Tip 2 unless you want to keep washing/drying the tips but you still need a coupler in this case. If you are using white icing to flood your cookie then you need another Tip 3 or even a bigger tip. If it’s just flooding (which refers to filling the whole cookie with icing) and you din want to use piping tip, I felt snipping off the end of the icing bag will also do the job! Just that you have to be careful when you go into small areas.
Initially I thought it’s not necessary to use piping tips for outlining and by snipping off the corner will do the job but being new, the piping tip really make a difference, it help to “guide” the icing to the right direction you want much better. In addition, I personally would prefer to use a coupler too, felt the grip is much sturdier too.
Hope these info help 🙂