What I've found as well as some others, is that sometimes
it's the car shampoo itself that causes the lack of slickness.
NXT, for example, is quite effective in the cleaning, but
I do notice a very reduced slick feeling. Does not matter if
i use a little or a lot in he bucket.
Some others that I have noticed having a similar affect are:
EO Wet car wash
Gliptone Wash N' Glo
PB prototype car wash (the high foam version was very effective as
well, and left a very clean, but not slick feel. The low foam/
high lubricity prototype offered much more slickness but less cleaning
power, imo. Often, i had to wash a surface twice to insure the
dirt and grime was totally removed. I haven't tried the
productiion car wash from them, so I do not have any reference
for that product.
Mequiar's Deep Crystal car wash (also cleaned well, but left the
paint feeling the worst of the car shampoos I've tried so far).
Products that I've found help keep up slickness in order or
most slick to least slick.These are my personal opinions so
YMMV:
PB Spray N Wipe: Works best on sealant LSPs
1z Perls (not a big fan of this product, but I do find that does
help retain slickness, due to leaving behind polymer protection)
Works best on sealant LSPs
FK1 PH Neutral car wash: Works equally well with sealants and
waxes
QEW Works equally well with sealants or waxes