have never done shrinking before , but as said , do not use to much heat , find the spot where the oil can problem is the worst by
finding the most "sloppy" area , use a piece of chalk and mark a circle around the bad spot , no need for oxy/acet , a simple lpg burner
will be fine , best done with two people , one to heat and the other with a dolly and maple malet at hand , old mate heats the area while
dolly is held underneath bad spot , you will see the metal rise in the circle , pull off heat and use timber mallet with dolly underneath to draw the metal in towards the center of circle , it does not take much , then once the area has been drawn in and slightly massaged
give the center of the worked area a tap with the timber mallet and then use a wet rag to shrink it.
You might find that you will have to "chase" it it a few times after planishing out the area done.
If you choose to weld up holes , hold a dolly under the area and "hot peen" the the weld while it is still red hot , this helps stop the "pulling" or distortion as the the weld shrinks as it cools which can pull things out of shape big time.