mt question is when do i need a grounging bushing, the one where a ground wire gets luged in the bushing ..... ive done it on commercial jobs but not really sure where i have to ....any code refrence would be good to ....thanks

One instance where they are required is when installing conduit or conduit fittings to service enclosures that have KOs, eccentric and concentric. If you were to knock out the largest KO, then I guess it would be the same as punching or drilling a hole, and no bonding-bushing or bonding-locknut is required.

250.92(B)

Use PVC for the nipple or conduit between the meterbase and disconnect/panel and avoid the whole ugly mess.

See 250.97 for voltages greater than 250 V.
They are treated similar to services.