i want to start doing some mudding and iam not sure what temp it should be in the garage,all i have is a little heater. Same for fiberglass too.

 

o and i 'am useing evercoat lightweight

 

I like it to be around 45F to 60F before I use any filler. It takes longer to set up in the cold, up here it can take a week before its sandable once the shop cools off again. I havent done fiberglass in the cold, only when it was relatively warm and around 70F outside.

Getting the metal warm really helps, but you should get the entire car warm rather than just putting a heat lamp in one spot.

 

Order one of these MrBuddy propane heaters! I used this (Big Buddy) one all last winter in the garage and it worked great. Works using the small camping style propane tanks or the larger BBQ type tanks. Has a built in fan, safety features, easy to setup and use. This heater would heat up a 1 & 1/2 garage from sub-zero temps to sweating-in-a-t-shirt temps within 20 to 30 minutes. It has 3 temp settings High, Medium and Low.

You'll not be able to use fiberglass unless you have some type of heat source that can maintain the air temp and the part your working on. A small plug-in heater will not work.

Filler is pretty much the same though its a bit more important for the part (sheet metal) to be warmed up as well. The air might be warm but the metal will take longer to warm up.