  In this article, we give a concise summary of $L_\infty$-algebras viewed in
terms of Chevalley-Eilenberg algebras, Weil algebras and invariant polynomials
and their use in defining connections in higher gauge theory. Using this, we
discuss the example of the string Lie 2-algebra in both the skeletal and the
loop model. In both cases, we show how to arrive at the twisted Weil algebras
which were used in arXiv:1705.02353 to construct a non-Abelian self-dual string
soliton, see also arXiv:1712.06623, arXiv:0801.3480, arXiv:0910.4001.
