Why not try to abuse the Painter for its own protection and use ALL blasts available. 50% of the blast are strong anyway as most of the metagame either play red or blue spells.

You can also use ponder/brainstorm to manipulate your library to find only the proper blast until you resolve of or your 8 painter servants (plus ponder/brainstorm) in your deck.

As soon as the Servant enters the game you can be the control deck for one turn. As soon as you untap you should be able to resolve the second combo part and either wait another turn or combo out immeditately depending on the matchup/situation. 20 counters and/or 16 instant "destroy target permanent" spells for one mana should be sufficient to protect your combo.

I donīt know if you will improve the deck when you "waste" slots to cards like CB/SDT/Trinket Mage/Fabricate...

This is I would try first:

"The Paint Shop" by MMD
4 Painterīs Servant
4 Grindstone
4 Ponder
4 Force of Will
4 Brainstorm
4 Blue Elemental Blast
4 Pyroblast
4 Red Elemental Blast
4 Pyroblast
4 Enlightened Tutor

4 Volcanic Island
2 Tundra
1 Plateau
3 Polluted Delta
4 Flooded Strand
2 Island
4 Ancient Tomb

You should be able to combo out on turn 4 constantly.

Turn 1: Enlightend Tutor/Ponder
Turn 2: Brainstorm/Grindstone/Ponder/Enlightend Tutor
Turn 3: Painter`s Servant/1-2 Blast
Turn 4: Activate Grinstone/1-2 Blast

You can certainly combo out on Turn 3 (even Turn 2) but this is neither realistic nor safe.

I am not 100% sure if the 8 Blue Blasts are really good enough and needs to be tested but I always wanted to build a deck around them and the Servant really abuses them best. Perhaps a combination of Orimīs Chant/Thoughtseize/Daze will stabilize/improve the deck. But I will definitely try the 16 Blast version first.