Pullets probably wouldn't have as much leakage as cockerels. It will probably vary by individual. Some may have very little and some may have a lot.
You wouldn't be able to get any pure Wheatens from Splash X Wheaten. Splash is really just Black diluted by two copies of the Blue gene, and Black tends to be very dominant, hence birds which are mostly diluted (Splash) black with small amounts of leakage. However, all offspring would be split for Extended Black and Wheaten pattern genes. So if you breed the offspring back to the Wheaten parent you would get 50% Wheaten patterned offspring (as well as 50% that will look like the birds from the original cross, so generally solid with a little leakage). The Wheaten might be a little "messy" but it should look generally Wheaten. This cross would also result in both Black and Blue offspring, so you would get Wheaten, Blue Wheaten, Black (with leakage), and Blue (with leakage) all from a second-gen cross.
RSL X Splash should give similar results. 100% Blue offspring with red leakage of varying amounts.
