Here we do a two stage deicing. We use diluted type 1 for deicing and then 100% type 2 for anticing. We used type 4 for the anticing stage for two winters, but found it difficult to get an even coating on the wing. It tended to come out in globs. Neat type 2 will produce a film on the wing quite easily. The type 4 has a better holdover time, but not by much, in fact I think that the quicker application of type 2 evens it out.