If a tree’s top growth is under threat, it may send out suckers from the lower part of its trunk in an effort to survive. This is often seen in ash trees that are under attack by emerald ash borers.

What your friend was most likely referring to was painting the tree with a 1:1 mixture of water and water-based indoor latex paint. This is what I use to paint the tree trunk and branches.

Purdue Landscape Report: Slime flux (also known as wet wood) is a dark, foul-smelling and unsightly seepage of sap from tree trunks (fig. 1).The disease is not usually a serious problem but the ...