writing with icing

[pud1]

i am doing my nans 90th birthday cake this week. have done a few kids character cake so i am fine with the fondant icing stuff but i have to write on the cake using icing. i am wondering how i am best doing this. i have seen tubes of icing int tescos that can be used. are these ok or is there an easier method. think i will be rubbish with an icing bag

If you use rolled icing i'd paint it with food colouring much easier,
The ones in tubes in supermarkets are bit to thick so try to make your own... Icing bag is possible if you have a proper one, cos when i bought a cheep one it was a total disaster.

thanks. how much will a decent icing bag be