Have you tried ice cold methanol overnight at -20?

try 1% formaldehyde or paraformaldehyde, will reduce the fluorescent background 

I tend to use 3% Paraformaldehyde:

1. Aspirate growth medium and replace with fixative 3% (w/v) PFA in PBS (optional: wash with PBS or equivalent before adding fix)

2. Incubate for 15-20min RT

3. Aspirate fix, add perm/quench, aspirate this and replace with fresh perm/quench.

Perm/quench: 50mM NH4Cl, 0.2% (w/v) saponin in PBS. Made up from 5M stock of NH4Cl and a 20% stock of saponin, both kept on the bench (saponin in the dark). If you don't want to permeabilise using saponin, then don't add it into the mix.

4. Incubate for 10-15min RT

5. Label with antibody in presence of saponin to permeabilise cells.

I tried both , pre-chilled methanol and paraformaldehyde (4%).

the major problem was that i lost most of the cells after fixing them with 4% parafomaldehyde and methanol as well.

Hello

All PDF here It will be very useful