sandwich ELISA

[Martin Offterdinger]

Hi
I need help setting up a sandwich ELISA for a transmembrane receptor,
that shows low expression. 
I tried to precipitate the receptor from a cell lysate using a plate
bound monoclonal AB and quantitate with a polyclonal AB followed by
staining with anti rabbit HRP. At the moment I do not get a specific
signal.
My questions are :

1 Will it be helpful to use the polyclonal antibody as the
primary(coat it to the plate) ?

2 What detergent should be used and in which concentration to
solubilise the cells??-At the moment I use 0.5% digitonin in isotonic
buffer. 
Do you think that different detergents would work better???
Thank you very much 
martin