Basically if u're a christian and feel offended in holding joss sticks, there isn't really a need to do so.
The 2 joss sticks (remember, take 2! Not 1, not 3 but 2!) and 3 bows doesn't mean u're 'praying' or 'worshipping' but a hallmark of respect to the deceased.
The red string which one finds in the plate is sort of like a 'lucky charm' to prevent wandering spirits from following u home. Basically, u take the string and wrap it around ur little finger only when u are about to leave and just before u reach home, u discard the string either on the roadside or in a bin.
And when u're leaving, there's no need to specifically go over to the deceased family members and inform them of ur departure. Simply leave quietly. This is what is traditionally practised.
No reds, no pinks, no oranges, no outlandishly punkish colours. Plain, simple dressing of black, white, dark or light colours.
Yes thats about it. Know it well. U are a Chinese I guess? It doesn't hurt to know such tidbit knowledge. More and more of the old practices and traditional ways of doing things are disappearing year by year.