The welding blankets are pretty nice to have. I have a few smaller ones that I got somewhere (marketed for something outside of welding, can't remember what). They are so slick no tape would stick to them, some super nylon or something. Anyway I would hold them in place with magnets. But the last one I got is from a welding supply and it is really nice to have. It is comforting to know I can toss it over my car if I am welding near by and it won't scratch the paint but protect it from flying sparks.
I burnt up a seat on an almost new Honda years ago while using something I shouldn't have and I learned my lesson.
Even with the welding blanket you don't want to it to have any big wrinkles that a spark from the MIG can get caught in. Those little red hot ball will even burn thru the welding blanket! It won't start on fire, but it will burn into or thru the darn blanket. So keeping the piece straight and flat so these balls can roll off is my best advice.
And of course the better your welds are,the cleaner the metal for example, the less sparks you will have.