Hi - fibroblasts tend to be pretty tough cells (one of the first cells into the wound environment whilst neutrophil oxygen bursts are going off) so they can take a lot of punishment. If I were you I would first try Ca PO4 precipitation (I used this on Rat-2 fibroblasts a long time ago with ~ 20-30% transductrion).
You can make up the components yourself so it is very cheap. There are a number of protocols on-line with ingredients etc. this link is just to the first one http://www.flemingtonlab.com/Protocols/ ... Transf.pdf