2004 merc e320 cdi bg probs

hi guys
im new to the board being tinting about 4 months now,so just really finding my feet,ive tinted roughly 12 or 13 cars to date,a full car could take me up to 4 hours to complete but i get there eventually,ive bought my self a mercedes e-class,to tint side glass has being straight foward but the b/g ive took 4 attempts at it and still about 3/4 way up on the left and right i keep getting small blister pop ups not at the matrix edge but about 3 inches in,they just wont stay down,could it be my baby powder dry shringing method or do i need to make my H shape lower or higher,getting really frustrated guys and theres no way im giving up and doing it in 2 or 3 pieces,any tips or pointers much appreciated!!

JST HEAT THEM UP WITH HEAT GUN FROM THE OUTSIDE,AND PUSH THEM OUT W/A TEFLON CARD

thanks for the reply,never tried that because i read on here that heating benz back glass could be dangerous,must give it ago,thought they were permanent so i kept binning the film

the defrosters are raised....steel wool the B-glass befor install...that should help alot...

If you heat from the outside ...dont heat the glass too much ...it will lay down.

thanks alot,ill try steel wooling it before install also