1.) Toy-Biz is out of business if you look at any of their kits you will know why.
(Missing parts, horrible fitting, etc)
2.) Not familiar with the primer and paints you use, can't comment on them.
3.) You can brush paint Figure kits, with one exception Skin-colour this is best airbrushed on.
Here is my process for painting figure kits(mostly anime/resin but will work for others too).
1.) I normally use a white primer, you will see why in a second.
1a.) Might second coat with Mr Base white.
2.) I mask the eyes and other areas and apply Flesh colour(mix your own differrent recipes for different genre and skin-tones).
3.) Apply a topcoat, this will protect your colours from mistakes and allow you to correct mistakes without touching the existing colour.
4.) Start painting your Kit and mask/topcoat as you go along, I go from light to darker colours. Lighter colours on top of the white basecoat.
5.) Last parts to be painted are the eyes, a habit I picked up over here.
6.) Hit the whole figure with a flat coat and pick out certain details with a gloss coat.
Using a White primer(Mr Base white) allows me NOT to use white on a figure and colours like yellow, red, etc. will get a brighter shine from it too.
For dark figures(aka matrix), creatures, etc I use gray or black primer.
Most colours can be touched up, Flesh I consider NOT among them.
Flesh is also a tough colour to handbrush on larger scale Items 1/12 and above you WILL benefit from any form of airbrush here. El Cheapo with canned air will do.
Another tip for filling tough fitting plastic figure kits, roll Putty(2 strip) into thin line and apply it to the poor fitting areas prior to joining, push/glue the parts togerther while the Putty is still moist. Excess will be squeezed our of the joint, Wipe excess off smooth with appropriate liquid for your putty and let dry. Remove seams as normal. Sand smooth when dry.
Advise for future:
Avoid Toybiz Kits like the plague.