When blending distinct colours on my lid, I try to lay all the colours down (as intensely as I'd like them) usually using my MAC #242 to "pack on" the colour.
If I'm using similar toned colours (e.g all pinks), I don't necessarily wipe the brush between colours, but I make sure to apply from lightest to darkest.
If I'm using distinct colours (e.g. blue and yellow) I definitely wipe the brush between colours! (Otherwise colours do come out muddy).
After the colours have been applied, I wipe the brush clean and very lightly sweep back and forth against the line where the colours meet. Sometimes I'll pick up a bit of one colour to blend it into the next (e.g. chrome yellow into electric eel). This helps to ensure that my colours stay intense. Alternatively, I look for a transition colour (like bitter for a chrome yellow/electric eel blend) and use that to facilitate my blending.
While I've found a lot of success with just a #242, depending on the look I may also employ a #217 (as it's a blending brush and just a bit softer!)
I love the #224 but I think that brush is best for blending out the crease and (at least for me) is completely useless on the lid.
With regard to bases, my simple recommendation would be to experiment. Blending on UDPP is a little more difficult than blending on a paint pot but I think UDPP makes colours SO intense (so learning to blend over that is a bonus).
Priss' recommendation about the "prime" is really helpful (but I'm also new to this and I don't quite have that down...LOL) Good luck!!